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UOG TOP PICK: Lightweight, highly packable and more confidence-inspiring than many ultralight shells, the Rab Phantom Mountain 2.5L Jacket strikes an excellent balance between low weight and dependable mountain weather protection. A top pick for fast hiking and lightweight backpacking in mixed conditions.
Rab says:
This is the ultra-packable shell that weight-conscious adventurers keep stashed in their pack year-round, ready for the weather to turn.
Whether you’re moving fast over challenging terrain or tackling treks where pack space is at a premium, you need a super stashable shell that will keep you dry in a sudden shower. Crafted from ultralight, 2.5-layer Pertex® Shield Diamond Fuse fabric, the Phantom Mountain Jacket has a weightless feel that won’t burden your pack, while offering the sturdy waterproof protection you need in unpredictable mountain weather. The Diamond Fuse technology uses yarns with diamond-shaped filaments to create a tough, abrasion-resistant fabric, ensuring the jacket withstands long distances being carried in your backpack. This balance of durability and effortless packability makes it the ultimate shell to keep stashed in your pack year-round, ready for thru-hikes, scrambles, and hut-to-hut treks.
Our Verdict
The Phantom Mountain 2.5L Jacket feels like a more practical evolution of Rab’s ultralight waterproofs. At 227g (Medium), it remains highly packable, but the move to a 30D Pertex Shield Diamond Fuse fabric gives it a more reassuring feel than many stripped-back emergency shells. It still packs down small enough to disappear into a rucksack, yet feels better suited to regular mountain use under pack straps.
The regular fit layers comfortably over a light fleece or midlayer without becoming restrictive, and the articulated sleeves move well when using poles or scrambling. I also like that Rab has included proper hand pockets and a more structured hood rather than chasing the absolute lowest possible weight.
Breathability is respectable for a lightweight 2.5-layer shell, though sustained steep efforts in humid conditions will still lead to some moisture build-up. For fast hiking, backpacking, and mountain days where low weight matters but reliable weather protection remains essential, this strikes a well-judged balance.
- Reviewed by Ultralight Outdoor Gear
Features
- 30D 2.5-layer Pertex® Shield Diamond Fuse fabric gives a weightless confidence, balancing durability with effortless packability
- 2-point hood adjustment, perfect for less extreme conditions or when every gram matters
- Stiffened and flexible polymer peak for increased weather protection
- Hood doubles as integrated storage pocket
- Optimised elbow precurve for unrestricted ascents
- Versatile full zip makes it easy to throw the jacket on and pull it off as the weather changes
- 2 external hand pockets with YKK® AquaGuard® zips
- Lightweight single sided rear hem adjustment with anti-snag tether
- Secure elasticated cuffs offer enough stretch to vent your forearms and access your sports watch
Specifications
- Small weighs: 218g
- Medium weighs: 227g
- Large weighs: 230g
- XLarge weighs: 244g
- HH: 20,000mm
- MVTR: 20,000 g/m2/24hrs
- Fit: Regular
- Centre back length (Size M): 75cm / 29.5inch
Material & Construction
- 30D Pertex® Shield 2.5-Layer construction with Diamond Fuse and fluorocarbon free DWR (73gsm)
- 100% Polyamide Woven Laminated Jacket Womens
