"The Patagonia R1 Vest fills the specific gap between a baselayer and a full midlayer jacket: core warmth with arms completely free for steep hiking or climbing approaches. It's unnoticeable in a pack on the approach and earns its place the moment the shell goes on. What Our Gearhead® Experts Are Saying:""I wear this under a shell on approach pitches where a full jacket would trap too much heat. The sleeves-free cut keeps my arms moving freely while the Polartec Power Grid holds core warmth without bulk."""