Best Climbing Belay Device
|Price||$129.95 at Backcountry|
Compare at 3 sellers
|$86.99 at Amazon|
Compare at 3 sellers
|$74.93 at REI|
Compare at 3 sellers
|$29.95 at Backcountry|
Compare at 3 sellers
|$49.95 at Amazon|
Compare at 3 sellers
|Pros||Anti-panic handle, top rope and lead modes feed smoothly, wide range of rope diameters (8.5 - 11mm)||Easy catch and hold, feeds slack smoothly, smooth lowering, handles ropes down to 8.5mm||Compact, safe and ergonomic way to pay out slack, a bit less expensive than GriGri||Great for belaying seconds on multi-pitch climbs, durable, good value||Three belay modes in on device, affordable, stainless steel inserts for greater longevity|
|Cons||Expensive, switching modes can be annoying, panic handle locks up easily||A bit clunky, can only use one rope, takes time to master techniques||Method of clipping to harness is counter-intuitive, unlocking device under tension takes some practice, easy to lower too quickly||Heavier than the Reverso||Slightly heavier than competitors, assisted braking mode requires learning a new belay technique|
|Bottom Line||Versatile assisted braking device with well-designed safety features||By far the most popular belay device in the world is also one of the very best||With a little practice this device quickly became one we enjoy using, with few, if any, downsides||Simple, durable, and optimal value for multi pitch climbs||A Top Pick because of its unique combination of three different belay modes in one small and convenient device|
|Rating Categories||Petzl GriGri+||Petzl GriGri||Trango Vergo||Black Diamond ATC Guide||Edelrid Giga Jul|
|Catch And Bite (30%)|
|Lowering And Rappelling (30%)|
|Feeding Slack (20%)|
|Weight And Bulk (10%)|
|Auto Block (10%)|
|Specs||Petzl GriGri+||Petzl GriGri||Trango Vergo||Black Diamond ATC...||Edelrid Giga Jul|
|Style||Active assisted braking||Active assisted braking||Passive assisted braking||Auto-block tube||Passive assisted braking|
|Recommended Rope Diameter||8.5 mm - 11 mm||8.5 mm - 11 mm||8.9 mm - 10.7 mm||7.7 mm - 11 mm||7.8 mm - 10.0 mm|
|Weight (oz)||7.1 oz.||6.3 oz.||7.1 oz.||2.8 oz.||4.3 oz.|
|Double Rope Rap?||No||No||No||Yes||Yes|
|Belay off anchor?||Yes||Yes||Yes||Yes||Yes|
|Assisted Braking?||Yes, active||Yes, active||Yes, passive||No||Yes, passive|
|Warranty||3 year||3 year||1 year||1 year||1 year|
Best Overall for Experienced Climbers
In 2019, Petzl updated the most popular assisted braking device in the world for a third time, releasing the newest version, now simply known (once again) as the GriGri. For those who are confused, this device updates the GriGri 2, which is no longer being produced or sold but is not at all the same as the original GriGri, with which it shares the same name. Although it looks very similar to its predecessor, this new GriGri has seen a number of minor tweaks, often incorporating aspects that were found to be successful with the release of the GriGri+ in 2017. The cam spring is a bit tighter, making it easier to pay out slack ATC-style, and the area on the back of the cam where you might hold your thumb to pay out slack is now lower profile as well, reducing the risk of holding this open when a leader falls. The lower arm now has a bit more play, making it slightly harder to simply open fully. Best of all, this device now accommodates ropes down to 8.5mm, which is currently the skinniest single rope on the market. These tweaks are minor but positive changes that only make this device function better.
While the GriGri is far and away the most popular active assisted braking device on the market, it still comes with the notable downside that one must lock open the braking cam to quickly feed slack to a leader, a design that has inspired countless competitors searching for better methods. With this model, it is easier than ever to "push" rope through the device, in the same way slack is fed with a tube style device, although the cam must still be overridden to feed out an armload or two in a hurry. Which brings up another downside of the GriGri — proper and safe belay techniques can be challenging to learn and perfect. Most climbers who have been at it a couple of years or longer have long since crossed this hurdle, and for them, we still recommend the GriGri as the best belay device on the market. For those who are new to climbing or inexperienced with a GriGri, or who simply like having even more safety features, we recommend the GriGri+ instead.
Read review: Petzl GriGri
Best for New Climbers
First released in 2017, the GriGri+ has several safety features not found on the standard GriGri, hopefully reducing the risk of belayer error accidents. This device works in the same way as the GriGri, but also includes a couple of clever overrides for the most common errors amongst GriGri users. The first is that the handle has an anti-panic feature. When lowering a climber, the belayer uses a lever-arm handle to release the grip on the rope. It is possible to open this handle way too far, without a hand on the brake rope, and suddenly drop the climber to the ground. With the GriGri+, the handle automatically disengages beyond a certain point, releasing the tension on the cam and stopping the lower. The sweet spot for a smooth, not-too-slow lower can be hard to find at first, but it's now much harder to drop a climber while lowering with a properly loaded GriGri+. The second feature is a toggle switch between lead and top-rope modes, which adjusts the spring tension on the cam inside the device. In top-rope mode, the cam grips far more tightly, while in lead mode, it allows for an easier time paying out slack.
While significantly safer than a standard GriGri, the features found on the + can be annoying to work around if you are so used to using a GriGri that it has become an extension of your mind and body. In particular, it is easy to forget to switch from top-rope to lead, resulting in a frustrated leader as they get continually short-roped. The new features also don't eliminate the need to lock out the cam while feeding out slack to a leader, a potentially dangerous moment, especially close to the ground. And the biggest hurdle to usage of the GriGri+ is that it can be challenging to learn to use properly and safely, an argument many die-hard ATC users cite as the reason they avoid the GriGri to begin with. This model is also heavier and more expensive than the standard model. While there are some downsides, GriGris have become nearly ubiquitous at the crag or in the gym no matter where in the world you are and offer tremendous advantages over standard belay devices. We believe that all types of climbers can benefit from knowing how to use a GriGri, and recommend the +, especially for those new to the game.
Read review: Petzl GriGri+
Best Bang for the Buck
Black Diamond ATC Guide
For climbers on a budget, and especially those that like to do it all, our recommendation is the Black Diamond ATC Guide. This device offers the same ideal characteristics as the simpler ATC XP for standard belays, while also providing auto-block capability for bringing up followers directly on an anchor. This tube-style device allows one to use the simplest, easiest to learn, and most commonly taught belay style for paying out slack while leading, negating the need to learn a new style based on the belay device. It also easily accommodates two strands of rope, making it ideal and versatile for rappelling — a huge bonus. While it isn't as inexpensive as the tube-style devices that don't have auto-block capabilities, we think that the extra couple of bucks for this ability greatly enhances the performance if you ever intend to do any multi-pitching at all.
The only real downside to the ATC Guide is that it doesn't include any form of braking assistance. Assisted braking devices reduce the likelihood of dropping a lead climber and also make it much easier to lock off and hold someone for long periods of time. Some passive assist devices are barely any more expensive, making them a compelling option instead. The ATC Guide is also slightly heavier than its closest and most popular competition, the Petzl Reverso, but we think the extra durability is worth adding a couple tenths of an ounce. If you want the most versatile option at a fantastic price, this is the one we recommend.
Read review: Black Diamond ATC Guide
Best GriGri Alternative that Feeds Slack Easier
As long as there have been GriGris, there have been imitation devices made by competing companies attempting to capture a bit of the market share, while also solving some of its inherent problems. While it has been a long time coming, the Trango Vergo is one of the most appealing active assisted braking devices we have tested. Its most endearing feature revolves around safety: it is not possible to lock out the catch cam mechanism, like on the GriGri. This feature alone greatly reduces the chances that a belayer could accidentally drop the climber while clipping, a problem even more dangerous when the climber is close to the ground. The cam that pinches the rope to provide the braking assist does not have a spring in it but uses the angle by which the rope is running over it to determine whether there is enough friction to catch or stay open. Feed out slack to the side as recommended, a method that allows one to pay out longer loops of slack with one arm, and the cam stays open. Pull upwards, in the direction that a climber would, and the cam uses friction to automatically lock up. The ergonomic design of the Vergo also allows you to hold the brake end of the rope in the same hand as the device without bending it back, so there is less friction to overcome when pulling out slack. Once mastered, we believe this method proves far easier and safer than lead belaying with a GriGri.
Of course, like all assisted belay devices, a new technique must be learned and mastered to be an effective belayer, especially for leading. Compared to the other active assisted braking devices, though, we found this technique to be relatively quick and intuitive to perform and didn't require much thought after only a couple of pitches. The Vergo also doesn't have the same anti-panic handle as the GriGri+ or Camp Matik, so it's possible to open it up full-bore while lowering and drop a climber very fast. The Vergo is only good to go with ropes 8.9mm and thicker, so beware if you commonly use an ultra-thin cord. Lastly, while Trango makes it clear in all its instructional documentation and training videos, it is easy to accidentally clip the Vergo into the harness the wrong way, which diminishes the amount of friction a leader puts on the catch cam. We found the correct way a bit confusing since it seems to be upside down if you are used to a GriGri's orientation, and puts a half twist into the belay loop when used correctly. Despite the minor downsides, the Vergo is our favorite active assisted braking device that isn't a GriGri. We highly recommend checking it out if you don't like the way the GriGri feeds slack or are curious about the other options out there.
Read Review: Trango Vergo
Ideal for Multi-Pitch Climbing
Edelrid Giga Jul
2019 saw the long-awaited release of the Edelrid Giga Jul, an updated version of the Mega Jul. The engineers at Edelrid worked hard to solve many of the problems with the older device, and the result has quickly become our favorite belay device for multi-pitch climbing. Most multi-pitch devices do not have braking assist, but so many climbers love the braking assist found on their GriGris that they will carry two devices up a multi-pitch climb rather than do without the added assistance. The Giga Jul awesomely negates that need by incorporating passive assist braking with standard tube-style functionality (what they call "manual" mode), combined with auto-block, for the most versatile belay device we have seen. A simple toggle switch allows you to reverse the device to switch modes. We found ourselves most often belaying the leader in assisted braking mode, although if the pitch is really easy and the climber is moving super fast, you can also just use manual. For rappelling, we prefer the smoothness of manual mode with a prussic backup, but we like how brake-assist rappelling is also possible. Of course, we pretty much always belay up the second in auto-block mode.
As with most great things, there are a few downsides. Belaying the leader with braking assist requires learning the technique, which we found to be pretty easy, but also takes slightly more effort than belaying in manual mode. Lowering a climber in brake assist mode can be a bit jerky, so we mostly prefer this device for multi-pitching, and use something else for our daily cragging. It's also slightly heavier and more expensive than a BD ATC Guide or Petzl Reverso, but this trade-off is minimal, considering you also get braking assist. For easy multi-pitching, many climbers may not need braking assist. However, for climbing anywhere close to your limit, where falls are a real possibility, having brake assist is a serious advantage, and the nifty Giga Jul gives you that versatility added on to the standard multi-pitch device features.
Read review: Edelrid Giga Jul
Excellent Emergency Backup
Wild Country Revo
The primary downside of all ATC or tube-style belay devices is that a firm grip is required on the brake strand of the rope at all times. If the belayer is hit by a rock, slammed into the wall, or the rope somehow slips out of their grip, a falling climber will hit the deck in about one second. Enter the new Wild Country Revo, which solves this issue by adding an automatic locking mechanism that stops the rope if it moves through the device faster than 4m/s. It does so by using an out of balance flywheel on the inside that combines with centrifugal forces to trigger the locking mechanism above certain speeds. The brilliance is that the device functions exactly like a simple tube, and the belayer uses the same simple belay technique they were taught when they learned. The Revo does not in any way assist with braking but simply provides an emergency backup, the first device that we are aware of that works in this manner. Because of this great design, its advantages include the smoothest paying out of slack of any device we have ever tried. It is also designed in a way that it cannot be loaded backwards, so no need to continually check for little hand and climber icons.
The principle downside to this device is that it can only be used with a single rope, much like most active assist devices such as the GriGri, somewhat limiting its appropriateness for multi-pitching. We would not use it to belay a second off the anchor from above. Compared to most devices, it is heavy and on the larger side, but not prohibitively so. It also comes with a price tag that you would expect from a complicated piece of engineering. Negatives aside, the emergency backup performed perfectly in all of our testing, and every climber who used it was amazed at its ease and simplicity to learn. We expect to see this device become significantly more popular in the near future, especially for gym climbing and single-pitch cragging.
Read review: Wild Country Revo
Why You Should Trust Us
This review is led by Andy Wellman, a Senior Reviewer at OutdoorGearLab since 2014. Andy is a lifelong climber with over 24 years of experience in all disciplines. Like most of us, his passion was kindled in the climbing gym, but soon carried him outside after beholding the mighty Diamond on Longs Peak and deciding he needed to up his game enough to climb it. He has climbed large alpine routes and big walls all around the world, from Peru to Alaska to Mexico to the Alps. He has also spent countless days perfecting his rock craft at classic sport and traditional areas such as Eldorado Canyon, Rifle, Smith Rock, and Yosemite while authoring and publishing numerous guidebooks along the way. He bases himself out of Ouray, Colorado, an ice climbing mecca, but which also has great cragging and quick access to many of the West's finest destinations and most stunning mountains. Assisting on many of these reviews is Cam Ring, another lifelong climber and former Yosemite Search and Rescue Member.
Every pitch climbed requires a belay device, and since our testers frequently get out on the rock many times per week, belay device testing is happening continuously. We spend lots of time staying up to date on the newest product releases, so we can purchase them and get to work testing. Each device tested for this review was thoroughly researched before being put into use, and this often involves watching YouTube and demonstration videos to grasp the proper technique for belaying with newfangled devices. We then practice our techniques before hitting the crag and belaying a minimum of 30 pitches with each device (but usually way more) before publishing our findings. We also teach other climbers and partners how to use each device and watch them learn and belay in order to notice problems, flaws, or benefits that we may have missed. The result is expert tested reviews and recommendations, rather than just a listing of a product's stats that anyone can glean off the internet.
Related: How We Tested Belay Devices
Analysis and Test Results
We begin the testing process by using each device for months in the field, and then finish up by comparative testing each device side-by-side, rating them on five metrics (catch and bite, feeding slack, rappelling and lowering, weight and bulk, and auto-block) based upon how they perform compared to the competition. The devices featured here are of three main styles: active assist braking, passive assist braking, and tube-style, so be sure to identify your own needs to help you narrow down the selection.
Related: Buying Advice for Belay Devices
Belay devices are important pieces of climbing safety equipment but can be confusing to master. This is one piece of gear where learning exactly how to use it properly is crucial. Improper use of a belay device may result in death or serious injury. It is very important that you read and carefully follow the manufacturer's instructions. We encourage you to visit the manufacturer's website and make sure you have their latest documentation for your particular device, as manufacturer's recommendations sometimes change over time as new safety guidelines are developed. Climbing is dangerous. Climb at your own risk.
A new belay device can cost anywhere from the price of a case of beer up to the price of a new rope! The low end of the price range is populated by tube-style devices, whereas the more expensive models are the active assisted braking devices. If you're looking for the best value out there, we've picked out a few that we consider exceptional. To begin, the Black Diamond ATC XP can't be beat on price and is a solid and reliable option, although we recommend the Black Diamond ATC Guide as another great budget buy because it is far more versatile with auto-block function at only a tiny increase in cost. Although they are expensive, high scorers like the GriGri are a great value due to their incredible performance.
This category measures and rates how easy it is to catch a fall with a belay device. Of course, every belay device here will catch a fall by arresting the rope provided they are used with proper technique, but due to their unique designs, the assisted braking devices tend to do this with more reliability and far less effort than a standard tube-style device. For instance, to catch a fall with a tube-style device, the belayer must lock the rope off down by their hip while also gripping tightly to the rope to keep it from slipping. With an assisted braking device, whether passive or active, the slightest amount of gripping pressure on the brake rope will provide the tension and friction required to lock up the device, holding the climber in place. This brings up another important consideration in this category: how easy it is to hold a climber locked off. Obviously, the assisted braking devices are supreme once again, and the ability to easily hold a climber for an unlimited amount of time with little to no effort is the number one argument for using one of these devices while climbing.
The final consideration for this metric is the range of rope diameters that a belay device is capable of gripping. Ropes on the narrow side can slip through some belay devices due to there not being enough friction if the design doesn't take narrow ropes into consideration. As the quality of rope manufacturing has increased, climbers are far more frequently using thinner ropes, with 8.9mm-9.2mm being much more common, and 9.5mm now being considered a reasonably fat "workhorse." The thinnest single ropes on the market today are only 8.5mm, so having a belay device that can handle these thin ropes certainly adds value. On the upper end of the scale, ropes over 9.8mm (especially ones that are a bit worn and fuzzy) create extra friction that can make it hard to force them through a belay device quickly and easily. As more and more climbers transition to thinner ropes, this is becoming slightly less of an issue, but once again, added versatility in regard to rope sizes only increases the value of a belay device.
The active-assisted belay devices that employ a spring-loaded cam to pinch the rope when it is under tension provide the easiest and most reliable catch. Due to their cam, they even allow a small amount of rope (a couple of inches at most) to slip through the device as they lock, which increases the dynamic aspect of a catch, reducing the forces on the climber, rope, and gear slightly. The devices that reliably catch like this are the Camp Matik, as well as the GriGri and GriGri+, and they received the highest scores. Both of the GriGris are also now capable of handling ropes down to 8.5mm.
Second best when it comes to this category are most of the "passive" assisted braking devices, like the Edelrid Giga Jul, Mammut Smart 2.0, and Black Diamond ATC Pilot. In "active" models, braking is created by a pinching mechanism inside the device itself; "passive" models rely on a pinch between the carabiner and the device to hold the rope. Passive models are thus dependent on this carabiner, and its shape and size can have a significant impact on performance (up to 35% differences in our tests). Always use these devices with the manufacturer recommended carabiner whenever possible (usually an HMS type), and expect that any deviance (along with changes in rope diameter) will affect its performance.
The standard tube-style devices, like the Black Diamond ATC models and the Petzl Verso and Reverso, are what scored the lowest compared to the rest of the field. These devices require substantial strength on the brake hand when catching a fall and continued lock-off when top rope belaying or belay your second.
Catching a falling climber is only half the duty of a belay device; getting that climber safely back to the ground is the other. That's where lowering and rappelling come in. Some of the devices we tested began with an automatic advantage in this category — the ability to rappel two strands. Those models are the ATC XP, ATC Guide, Verso, Reverso, and Giga and Mega Juls. Shoppers should recognize that none of the active assisted locking devices can rappel a doubled rope, nor can the passive ClickUp+, Black Diamond ATC Pilot, or Mammut Smart 2.0. Consider these models only for single-pitch routes or multi-pitches in combination with a two-strand device.
The difference in lowering/rappelling scores comes down to the smoothness of the action and the range it is good for. We saw the most consistently good performance from the tube devices, as well as the Wild Country Revo. Although the assisted braking models all provide the ability to lock the device and rest hands-free, they often exhibit narrow ranges and jerkiness when lowering.
The standout performance from assisted braking devices comes from the GriGri. It lowers smoothly and jerk-free, largely due to the absence of an anti-panic mechanism. The GriGri+, Camp Matik, and Edelrid Eddy all have anti-panic levers. If you pull back too far on the lever, the unit locks up. While this is to prevent someone from accidentally dropping themselves or their partner, it creates a narrow window between lowering and locking up. The Matik and Eddy locked up more than the GriGri+, but all require a deft hand that does improve with practice. These devices are unquestionably safer for lowering partners but can also be perceived as more annoying to use.
The passive assisted devices have some of the poorest lowering action. We often find them jerky when compared to tube devices. However, because you need to push and pull on them quite a bit to lower your partner, they are quite safe to use and lock up as soon as you let go.
Feeding slack is a category we include to measure each device's usefulness for belaying a lead climber. A lead climbing belay requires more attentiveness and rope management skill than a top-rope belay. The ability to take and give slack quickly and precisely is important to ensure a good belay — especially when close to the ground. The most important thing to consider is how easily and safely you can feed slack without the device locking up. Devices that lock up on a hair-trigger are very difficult to master and are the cause of many lead climbers' frustrations as they are continuously short-roped by their belayer. A secondary consideration, since we are all guilty of making mistakes, is how easy the device is to release once locked up so that slack can be fed quickly again. When a climber is yanking for rope, desperate to make a clip before falling, and the device locks up, being able to quickly release it can make a difference between success or an extra-long fall.
Tube devices require the simplest motion to take or feed slack and receive the best scores in this category because of it. They are also the easiest to learn how to use and are most climbers' introduction into belaying. While it is not technically a tube, the Wild Country Revo functions just like one and is far and away the highest scorer when it comes to smoothly paying out slack. This is due to the wheel that the rope runs over, which greatly minimizes friction. It doesn't include any breaking assist that might accidentally lock, but it does have an emergency lock-up feature that we were never able to trigger while simply feeding out slack.
When it comes to the passive and active-assisted braking devices, results were more mixed. For the passive devices, we like the Edelrid Mega Jul and the Mammut Smart 2.0 the best. They use similar movements to tubes but require upward pressure on a handle or loop to disable the device's locking mechanism when feeding out slack quickly. The Smart 2.0 needs only a little upward pressure to prevent it from locking, whereas the Black Diamond ATC Pilot requires substantial and continuous pressure. The Climbing Technology ClickUp+ requires using a tube-style method of feeding out slack but is very quick to lock up and difficult to unlock quickly compared to others.
The active assisted braking devices have some of the more complex methods for giving slack quickly, and each features a different method. The Trango Vergo has the most ergonomic and smooth feeding design of any of these devices and does not require overriding the camming system to feed out slack, a nice safety feature. The Petzl GriGri and GriGri+ feed slack well with little friction but often require a technique that can reduce the device's safety, especially if the climber is close to the ground. These devices can also be hard to master for people with small hands, which may include children. The Edelrid Eddy and Mad Rock Lifeguard have more friction, making it challenging to pay rope out quickly. The Camp Matik uses a unique "pistol" grip design, which does take some getting used to if you've belayed differently for years.
Like all climbing gear these days, belay devices are getting lighter and smaller. Weights range from 2.0 to 13.0 ounces. Whether the weight is a critical component for you depends on a few things: whether or not you are climbing with your device on your harness, and whether or not you appreciate the "training" weight in your backpack.
When it comes to something you're likely to carry on your harness, the Edelrid MegaJul, Petzl Verso and Reverso, and the Black Diamond ATC XP are the lightest options. The ATC Guide adds another ounce to your harness but not much more bulk. Among the active assist braking devices, the Mad Rock Lifeguard is a decent alternative for those that like to multi-pitch climb with a GriGri. It's only a little bit lighter but a lot more compact. Some of the highest performing devices, such as the Revo and Giga Jul, are also a bit heavier than their closest competitors, forcing one to choose whether saving an extra ounce or two is worth compromised performance, or whether ideal functionality is worth a small penalty in weight.
Auto Block (Resistance Belaying a Second)
Belaying a second directly off the anchor is a convenient way to ensure a reliable catch and a comfortable belay during multi-pitch climbing (be sure to read the manufacturer's instructions carefully, as this type of belay configuration is more complex and mistakes can result in death). Most of the devices we have tested offer some way to do so, and we have noted this in the specs table in the chart at the top of this article. Unfortunately, though, belaying in this manner can create substantial friction with many of the device designs that can exhaust a belayer's shoulders and elbows, and in extreme usage, like for mountain guides, can lead to tendonitis.
Our grading for this metric considers whether a device is capable of being used this way or not and whether it is easy to set up or very confusing and challenging. Some of the devices require being set up in a way that is not at all intuitive. Secondly, we assess for versatility, scoring models that can accommodate two ropes a bit higher. Lastly, we took into consideration the amount of friction in the system, which affects the amount of energy it takes to belay in this manner, with the smoother devices being preferred.
When assessing for friction, we noticed how each device felt while out on multi-pitch climbs, but also wanted some more concrete results, so we compared one device after another on a mock anchor, noticing the differences in the amount of friction we had to overcome to feed the rope through the auto-blocked device. Both of the GriGris performed especially well in this regard, as did the Camp Matik. In our comparative testing, many of the most popular and commonly used auto-block tubes also had some of the highest amounts of friction to overcome, which is slightly disappointing. The ATC Guide and Petzl Reverso have quite a bit more friction than the GriGris, but even worse is the Edelrid Mega and Giga Jul, and worse still is the Mammut Smart 2.0.
Choosing a belay device is not an easy task, but the first step we recommend is assessing your own needs. Next, consider what techniques you already know and what techniques or resources you have for learning a new belay style. Answering these questions will help you determine if the investment in an active assist device is worth it, or whether you might prefer a passive assist device instead. Be sure to pick up a tube-style device if you plan to rappel or multi-pitch climb. We hope the information provided has been helpful in your search.
— Andy Wellman & Jack Cramer