The Men's Patagonia R1 Fleece Vest is durable, stretchy, and breathable. Polartec Power Grid fabric is hybridized with the Capilene Thermal Weight base layer fabric to reduce bulk and make this lightweight layer even lighter, with HeiQ Pure odor control to keep things fresh. Hybrid design boosts warmth around the chest and shoulders, while improving back and underarm breathability and venting extra heat.