At first glance the Mythic is an incredible sleeping bag. Rab combines premium 900-fill power down, silky Pertex Quantum fabric, and a minimalist zipper to create a bag that's plenty warm yet also ultralight. But when you step back and compare it with other ultra-premium bags, it doesn't look quite as good. Under closer inspection, the tiny zipper saves weight but is prone to snagging. Moreover, the short zipper length limits your ability to vent excess heat on warmer nights. Its spartan dimensions also contribute to its low weight but can be uncomfortably constrictive for larger folks or side sleepers.
Rab Mythic 400 Review
Compare prices at 2 resellers Pros: Ultralight, lofty 900FP down, packs small, solid warmth, waterproof stuff sack
Cons: Short half-length zipper that's prone to snagging, narrow leg dimensions, one size "fits" all
Compare to Similar Products
Rab Mythic 400
|Price||$374.96 at Backcountry|
Compare at 2 sellers
|$470.00 at Backcountry|
Compare at 2 sellers
|$429.00 at Feathered Friends||$389.00 at Feathered Friends||$149.96 at Backcountry|
Compare at 3 sellers
|Pros||Ultralight, lofty 900FP down, packs small, solid warmth, waterproof stuff sack||Spacious dimensions, super comfortable, great loft, lightweight, made in the USA||Super lightweight, incredible loft, snag-proof zipper, cozy hood||Best-in-class zipper, best-in-class hood, awesome loft, great warmth-to-weight ratio||Awesome warmth-to-weight ratio for the price, very compressible, tons of venting options, nice compression sack included|
|Cons||Short half-length zipper that's prone to snagging, narrow leg dimensions, one size "fits" all||Expensive, awkward hood, good but not great zipper||Uncomfortably narrow dimensions, bare-bones design, noisy fabric||Narrow leg dimensions, no draft collar, heavier and bulkier than some 3-season options||Not as warm as its temp rating, no draft collar, uncertain durability|
|Bottom Line||A premium bag that's designed to minimize weight and packed size.||The only ultra-premium bag to combine low weight, good packability, and luxurious comfort.||Our favorite when ounces matter, this is a full-size mummy bag that's both warm and ultralight.||Our favorite zipper and hood in a bag that's also exceptionally warm and lofty.||An exceptional deal for a lightweight bag that excels in wet conditions.|
|Rating Categories||Rab Mythic 400||MegaLite||Hummingbird UL 30||Swallow 20 YF||NEMO Kyan 35|
|Packed Size (15%)|
|Features & Design (10%)|
|Specs||Rab Mythic 400||MegaLite||Hummingbird UL 30||Swallow 20 YF||NEMO Kyan 35|
|Insulation||900 FP Down||850+ FP Down||950+ FP Down||900+ FP Down||Synthetic - Primaloft Silver|
|Compressed Volume (L)||7.3 L||7.2 L||7.3 L||8.5 L||6.6 L|
|Measured Bag Weight (Size Long)||1.49 lbs||1.62 lbs||1.45 lbs||1.94 lbs||1.89 lbs|
|Compression/Stuff Sack Weight (oz)||1.5 oz||1.6 oz||0.8 oz||1 oz||2.4 oz|
|Manufacturer claimed weight of size Regular (lbs)||1.44 lbs||1.5 lbs||1.33 lbs||1.79 lbs||1.69 lbs|
|Manufacturer Temp Rating (F)||21||30||30||20||35|
|EN Temp Rating (Lower Limit)||21||Not rated||Not rated||Not rated||35|
|Fill Weight (oz)||14.1||13||12||17.5||12|
|Shell material||Pertex Quantum (10D)||Extremelite (12D)||Pertex Endurance (10D)||Pertex YFuse (20D)||Ripstop nylon (20D)|
|Small Organization Pocket||No||No||No||No||Yes|
|Zipper||Half-length / Side||Full-length / Side||Full-length / Side||Full-length / Side||3/4-length / Side|
|Shoulder Girth (in)||55||64||58||60||62|
|Hip Girth (in)||41||Unknown||52||56||57|
|Foot Girth (in)||33||39||38||38||46|
|Compression or stuff sack included?||Stuff (Waterproof)||Stuff||Stuff||Stuff||Compression|
Our Analysis and Test Results
When comparing the Mythic 400 with its competitors in the backpacking sleeping bag review, it's essential to factor in that the Mythic we tested was a size regular while all the other bags were size long. This does make the comparison more difficult, but it was our only option because the Mythic only comes in one size. Fortunately, a Rab size regular was just long enough for our 6'2" lead tester. Anyone 6'3" or taller, however, will likely be happier in a different bag.
To keep you cozy the Mythic 400 is filled with 14.1 ounces of premium 900 fill power goose down. It also features a small neck baffle and half-length zipper to seal the heat in. With this insulation and features, it receives an EN lower limit temperature rating of 21°F.
Our testers felt this rating was accurate compared to other EN-rated bags. However, the unrated Western Mountaineering MegaLite and Feathered Friends Hummingbird, which both receive 30° ratings from their makers, seemed to be slightly warmer.
The Mythic 400 is optimized for minimum weight. To accomplish this, it features high fill power down, thin 10-denier Pertex Quantum shell fabric, and a tiny half-length zipper. A size regular tipped our scale at an impressive 1.49 pounds.
We were surprised, however, because this meant the Mythic was slightly heavier than a size long Feathered Friends Hummingbird—a warmer bag that also includes a burly full-length zipper. Overall, the Mythic is still ultralight, with an outstanding warmth-to-weight ratio, but the even lighter Hummingbird bests it.
One aspect of this bag that's compromised to achieve its low weight is its comfort. The Mythic 400 features some of the narrowest dimensions of any bag we tried. Testers specifically complained about the lower end of the bag feeling constrictive. We were big fans, however, of softness of its liner fabric and cozy loft of its premium down.
This bag is the only one in the review that comes with a waterproof stuff sack. Although this sack isn't quite as good at compressing the bag as an aftermarket compression sack, it performed better than the other simple drawstring stuff sacks we tried.
Using an aftermarket compression sack we measured its minimum compressed volume at 7.3 liters. This is better than average but not as small as its low weight would suggest.
The performance area most compromised by this bag's desire to be ultralight is its versatility. Our testers found the minimalist half-length zipper to be ineffective at venting excess heat on warmer nights.
In addition, the trapezoidal baffles that hold its down are not continuous. This eliminates the possibility of moving down from the top to the underside of the bag to adjust the level of insulation. Other ultra-premium bags with continuous horizontal baffles, like those from Feathered Friends, Western Mountaineering, and Marmot, possess a distinct versatility advantage.
Factoring these drawbacks in, we are most comfortable recommending the Mythic 400 for lightweight missions within a narrow temperature range of overnight lows between roughly 25° and 45°F.
Features and Design
This bag is clearly designed to be ultralight, and all superfluous features have been stripped away for this purpose. Despite these sacrifices, however, it still weighs a couple of ounces more than the warmer, cheaper, and more versatile Feathered Friends Hummingbird. We still like the Mythic's high-quality materials and construction but feel like it doesn't strike a bullseye on what seems to be its overarching design goal.
The Mythic is ideal for any application where you hope to go truly ultralight. For thru-hikes or other long trips, however, its versatility limitations might be frustrating to deal with.
Due to its ultra-premium down this bag comes with an ultra-premium price tag. However, compared to the other $400+ bags the Mythic doesn't stack up particularly well. In fact, for most outdoor applications, our testers would prefer one of the other high-end bags. For this reason, we consider this bag to rank toward the bottom of the stuff sack in value.
The Rab Mythic 400 is ultimately a victim of the high expectations set by its high price. On its own, it's an incredibly light and well-made bag. But in direct comparison with other ultra-premium sleeping bags, its deficiencies in comfort and versatility become more apparent. As such we can only recommend it for ultralight travelers if they can find it on sale.
— Jack Cramer