Hands-on Gear Review

REI Flash 45 Review

By: Brandon Lampley ⋅ Review Editor  ⋅  Jan 31, 2016
Price:  $150 List  |  $149.00 at REI
Pros:  Cheap, lots of external storage
Cons:  Mediocre carrying comfort, poor weight-to-volume ratio, poor design for main pack pocket
Manufacturer:   REI

Our Verdict

The REI Flash 45 is one of the most affordable packs we tested, but it unfortunately performed so poorly we have a hard time recommending it over much higher performing competitors. The weight-to-volume ratio is poor and the very flexible simple frame does a poor job transferring weight to the waist belt. On the plus side, it is cheap.

The Flash competes most closely in volume and features with the three highest scoring overall models. The Editors' Choice Gossamer Gear Gorilla and the Best Buy Osprey Exos 48 are both much better packs.

Our Analysis and Test Results


The REI Flash 45 earned below average scores in all of our metrics with the exception of features. It includes a lot of our favorite pockets and straps, but with interesting and not always useful departures from common construction.

Performance Comparison

Logging some miles with a 25 pound load in Rocky Mountain National Park.
Logging some miles with a 25 pound load in Rocky Mountain National Park.

Weight-to-Volume Ratio

This pack is available in medium and large torso lengths; our test model was the large version, which was appropriate for our 5' 11" lead tester.

Weight Bottom Line:
Total Weight with all modular components = 2 lb 3.5 oz
Pack stripped of components = 2 lb 0 oz

Lid = 3. 5 oz

While you could remove the frame from this pack, we do not recommend it.

The Flash's exterior pockets hold a lot of volume  but can dump out your gear when you disconnect the straps to access the main bag.
The Flash's exterior pockets hold a lot of volume, but can dump out your gear when you disconnect the straps to access the main bag.

OGL Measured Volume Bottom Line:
Total Volume = 49 L
Main Bag = 35 L
Front + Side Pockets = 8 L
Lid = 6 L

Unlike all the other packs we tested, the side and front pockets on this pack are not separated, but rather form one large, continuous mesh storage pocket. More about this below in features. At 20 g/L for both max and stripped of its lid, the Flash earned one of the worst scores for average weight-to-volume ratio. Even the more fully featured Exos 48 has a better ratio.

Load Carrying Comfort

This product didn't overly impress us in carrying comfort; we judged it "Good" at carrying both 15 and 30 pound loads. The flexible Delron rod that forms the side frame doesn't function as well as more rigid minimalist frame systems for stabilizing your load.

The Flash accepts this 25 pound load with room leftover  but doesn't carry it that well.
The Flash accepts this 25 pound load with room leftover, but doesn't carry it that well.


The Flash 45 is one of the most featured models we tested, with some strange departures from common construction. The main pack closes with a simple drawstring and is topped with a removable floating lid. Unlike all the other packs we tested, the external storage is one large wrap-around mesh pocket. At first glance, it appears to be two side pockets and a main front pocket, but no, it's actually just one big external pocket. We found it hard to get our water bottles to stay put on the side. There are no lower compression straps on this pack, just one each side near the top.

The Flash has a large free-hanging pocket inside that accepts a hydration bladder and a mitten hook on a sewn-in loop at the top to secure it. A center port allows you to route the drinking hose over either shoulder.

A shoulder strap pocket is one of the awesome features on the Flash. However  we did not find the unique side pocket construction beneficial.
A shoulder strap pocket is one of the awesome features on the Flash. However, we did not find the unique side pocket construction beneficial.


This pack earned a low adaptability score. While there are side compression straps and exterior lash options, we found them not very useful. If you need to get into the main pack, you must disconnect at least two of the buckles that are likely holding your externally stored gear in place. It's possible to dump your whole exterior load just because you need one item from inside the main pack. In addition, no lower compression straps mean that low volume loads carry poorly by filling the bottom of the pack.

Without compression straps for the lower portion of the main bag  smaller loads carry awkwardly  filling the bottom and leaving the upper portion of the pack empty.
Without compression straps for the lower portion of the main bag, smaller loads carry awkwardly, filling the bottom and leaving the upper portion of the pack empty.


The Flash 45 earned a low score for durability. We'd recommend the Gorilla or Hyperlite Mountain Gear Windrider 3400 if you want a similarly sized pack that is more durable.

Best Applications

This REI backpack is not the best pack for any niche we can think of. Our three award winners each fit a niche along the ultralight backpacking spectrum.


This bag is often on sale at up to half of its retail price. If your budget is very limited, it'll get the job done til you can save up for something better.


With a poor weight-to-volume ratio and the least utilitarian set of features, the REI Flash 45 scored at the bottom of our field of contenders.

If it's all you can afford  the Flash will get the job done. However  we'd recommend saving up for a better performing ultralight pack.
If it's all you can afford, the Flash will get the job done. However, we'd recommend saving up for a better performing ultralight pack.

Brandon Lampley

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OutdoorGearLab Member Reviews

Most recent review: June 20, 2016
Summary of All Ratings

OutdoorGearLab Editors' Rating:  
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Average Customer Rating:  
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67% of 3 reviewers recommend it
Rating Distribution
5 Total Ratings
5 star: 20%  (1)
4 star: 0%  (0)
3 star: 40%  (2)
2 star: 40%  (2)
1 star: 0%  (0)

1 of 1 people found the following review helpful:
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   Feb 8, 2016 - 10:11pm
Midwest Mike · Backpacker · Chicago

Or, more specifically, I would recommend it to a friend who like me has a very limited budget and otherwise has lightweight gear. I don't disagree with anything in the review, but I was able to replace my old external-frame heavyweight for about $55 with a sale + 25% off coupon. I'm glad I did. I tend to go on long weekend trips; my base weight is probably about 10 pounds plus the pack. The pack keeps the weight off my hips and works to hold my gear, and I go out and have a great time.

None of which is to say that I wouldn't buy something from Gossamer Gear or ULA if I had the cash. Maybe I just don't know what I'm missing. But I'm more than happy with the Flash for now.

Bottom Line: Yes, I would recommend this product to a friend.


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   Jun 20, 2016 - 10:58pm
Bug Juice · Backpacker · CO
Lightweight and Full Featured

This is a fantastic lightweight, full featured pack capable of carrying a thru-hiker load if you can pack efficiently. I have had many packs over the years and each one seems to either represent improvements in technology and/or serve a specific need.

Weight: At just over 2-pounds (1kg exactly), it was a nice weight reduction over my 5 year old Flash 55 (which weighs ~30% more), plus the 45 has just enough bells and whistles (litterally…the sternum strap has a built in whistle) to make you feel as though you are not sacrificing functionality.

Sizing: As far as sizing goes, I would suggest sizing up compared to what most people are used to. I'm 5'10", 155 lbs with an average torso length and the Large was very comfortable ( medium could have worked too ). If you are a bigger person the large will likely feel to small. An added benefit of sizing up i(f the fits is comfortable) is that the pack grows to 50 liters (per the tag), so it gives you a bit more space.

Load Capabilities: I used this pack most extensively on a 220 mile JMT through hike. My base weight was 15 lbs and when I added the largest food drop and full water I was ~33 lbs. At this weight the pack was definitely just beyond it's comfort limit for me. A couple days later when my food supplies had been reduced it was no problem, so I would say to plan on no more than 30lbs for optimal comfort. A typical bear canister (BV-500) fits vertically without any issues but will not fit horizontally (smaller sizes would). The rest of my gear for this trip basically all fit inside the main compartment (and top pocket) …needs to be compressible gear and efficiently packed. The gear I had on the outside mesh pockets were tent poles and water bottle/hydration bladder.

Features: Considering how lightweight the pack is there are quite a few features you don't typically find… The 2 small mesh pockets on the hip belt are indispensable for things like camera/phone or gps as well as pocket knife, lighter, lip balm. The top pocket holds quite a bit more…perfect for lunch, maps, steri-pen/filter, etc. There is also a small pocket on the shoulder strap which was great for keeping energy bars or sunscreen. Also, the underside of the top pocket has another access compartment (with a key hook). There is a hydration sleeve and hose port inside the pack, but I didn't find these very useful because a bladder would take up too much room in the main compartment and was too difficult to get out when the pack was full. Instead I used the mesh pockets on the outside which worked great.

The exterior of the pack is basically covered in stretch-mesh, which is common for ultralight packs. The sides have openings cut in them so I could easily access a water bottle or other items while walking… I thought this was a great design feature. The mesh is also a good place to stash a wet tarp or rain jacket for quick access. The hip belt had sufficient cushioning as well as on the shoulder pads (until overloaded). There are lightweight metal stays to help transfer the load to the hip belt, but there is no rigid backsheet. The back panel has cushioning that attempts to provide ventilation without much luck. I also had to pay special attention to how I packed everything so I wouldn't feel the bear canister through the back panel (sleeping pad strategically placed solved the problem). There are load lifters but they really needed due to the compact design.

Durability: Everything seems to be holding up nicely. The nylon on the bottom of the pack shows some wear from setting it on the ground with the hard bear canister on the bottom. A small plastic buckle cracked on the release tab (doesn't effect usage). The only other issue I had was the sternum strap seemed to keep working it's way up but not uncomfortably…more of a design flaw.

Value/Overview: At the full retail price ($130) this is a great deal and even better when they had it on sale for $80! Comparable lightweight packs that would perform similarly could easily cost $250-$300. If you have, or are committed to getting, an ultralight backpacking kit this pack will definitely handle things well for weekend or longer trips. On the other hand, if you are just starting to go in the ultralight direction I'd recommend buying other gear first (sleeping bag/pad) because this pack won't handle the volume or the weight.

Update: I'm currently 1400 miles into an AT thru hike with the same pack. It's holding up great!

Bottom Line: Yes, I would recommend this product to a friend.


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   Feb 9, 2016 - 07:25pm
Lpft · Backpacker · California

The review is spot on about the main drawbacks of the backpack.

The lack of lower compression makes it useless for sub-full loads, and the large mesh compartment is just a hassle when the bag is open.

The drawstring has a tendency to snag as well, anyone with a flash 18/22 will be familiar with.

That said, I got mine for ~$50, and at that price it made for a very quick and easy light backpack.

Personally found the comfort a bit better than the exos on the lighter loads(sub 25lbs).

Bottom Line: No, I would not recommend this product to a friend.

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