Rab Mythic Ultra 120
Summary
Price At Time Of Writing | $465.00
Our Overall Rating | 90 out of 100
Pros - Lightweight, warm
Cons - Less versatile, mummy shape, half-length zipper
Overall - A sleeping bag for weight-conscious adventurers
Technical Specifications
Packed Size - 12.6x6.3in
Weight - 11.6oz
Fill - 900-Fill Power European Goose Down
Our Analysis & Ratings
The Rab Mythic Ultra 120 is a great, ultralight sleeping bag built for serious fast-and-light adventurers who want maximum performance with minimal weight. At just 330g, this bag pushes the limits of warmth-to-weight ratio, combining cutting-edge insulation technologies and sustainable materials. Designed with activities like thru-hiking, bikepacking, alpine trekking and mountain running in mind, it’s best suited for those who need their gear to be efficient, compact and reliable. While its minimalist features may not appeal to casual campers, it offers exceptional value for those wanting something packable and versatile.
Comfort - Despite its ultra-minimal weight, the Mythic Ultra 120 delivers a surprisingly cozy sleeping experience. The 900-fill power European duck down provides a lofty, soft interior feel, and the 10D nylon lining is breathable and smooth against the skin. The tapered mummy shape wraps snugly around the body, minimising dead air and improving heat retention, while the anatomically shaped footbox offers just enough space to avoid that cramped feeling. Side and back sleepers will find the design tolerable, though it naturally favours those who sleep still. The snug hood offers decent coverage, although pairing it with a larger pillow can be a little awkward due to size mismatches. Overall, the bag hits the comfort marks impressively well for something this light.
Construction - Rab has gone all in on materials and design here. The Mythic Ultra 120 features ultra-light yet durable 7D ripstop nylon on the exterior and a recycled 10D inner lining treated with TILT (Thermo Ionic Lining Technology). TILT reflects radiant body heat back to the sleeper, boosting warmth without adding weight. The hydrophobic down fill is treated with Nikwax’s fluorocarbon-free water-resistant coating, so it continues to perform even in damp environments. The bag also includes well-stitched loops on the underside to securely attach to compatible sleeping pads like Rab’s Ultrasphere. During our field testing, we didn’t experience any down leakage or signs of fabric wear, even when using it directly on rocky terrain. The build feels trustworthy, despite its featherlight form.
Features - While features are intentionally stripped back to keep weight down, the Mythic Ultra 120 is still smartly designed. The standout is the integration of TILT technology, which enhances thermal efficiency without any bulk. The half-length YKK zipper includes an insulated baffle to reduce cold spots and anti-snag tape makes operation smooth. There’s a draft collar and a shaped hood to retain warmth around the head and neck. Though we’d personally prefer a longer zipper for better ventilation and ease of use, we understand this was sacrificed for weight savings. The bag also comes with a lightweight compression sack and a mesh storage bag. For modular users, the ability to strap the bag to a sleeping pad adds versatility and makes sure you don’t slide off your mat at night.
Size/Weight - The Mythic Ultra 120 is among the lightest down sleeping bags on the market, weighing only 11.6oz. Its packed size is listed at 12.6x6.3in, though we found it compresses even smaller (closer to the size of a large grapefruit (roughly 6in diameter)), making it great for ultralight pack setups. It comes in regular and long sizes, so people up to 6’6” should find a decent fit. We used the regular version with a pad and stayed comfortably warm during late June nights. While ultralight packers will appreciate the small footprint, casual users might find it too narrow or restrictive compared to more relaxed designs.
Versatility - This bag is firmly targeted at three-season ultralight use. Rab rates the bag’s lower comfort limit at 32°F when paired with an R4-rated pad, though it held up well on cooler nights even with a slightly lower R-value mat. It's most effective for summer alpine trips, late spring and early autumn adventures. Thanks to its reflective lining and high fill power, it punches above its weight in terms of warmth. Just note that it’s not meant for deep winter use or those needing extra room for layering inside the bag. The modular strap system adds flexibility to pair with different pads, but beyond that, it’s a stripped-down, focused piece of gear. Casual campers or those wanting year-round versatility will need to look elsewhere.
Overall - The Rab Mythic Ultra 120 is built for adventurers who count every gram but still want reliable warmth and insulation in unpredictable alpine and three-season conditions. The mix of 900FP hydrophobic down, recycled and responsibly sourced materials, and the innovative TILT lining all come together in a bag that feels premium and purpose-built. While the half-length zip and snug mummy fit won’t be to everyone’s liking, the Mythic Ultra 120 isn't trying to be everything to everyone. It’s for fast-and-light purists: bikepackers, mountaineers, ultralight hikers and anyone who treats weight savings as critical. If that sounds like you, the Mythic Ultra 120 is hard to beat.
