Weighing less than half a pound, the Rab Women's Phantom Mountain Jacket is an ultralight, hyper-packable shell designed for gram-counting thru-hikers and hut-to-hut trekkers. Its 2.5-layer Pertex Shield Diamond Fuse fabric offers surprisingly high waterproof, breathable ratings for how compact the shell packs down. A regular fit lets you layer over whatever you're wearing whenever you feel a raindrop, and precurved elbows keep your stride in line with full mobility. There are two points of adjustment at the hood, and a single-sided hem adjuster stays secure under backpacks and harnesses.