Patagonia Capilene Thermal Mid Weight Half Zip-Neck The greatest breathability and warmth in any polyester baselayer made by Patagonia with minimal bulk. - Polartec Power Grid fabric has a smooth face for easy layering; fabric’s open grid pattern next to skin provides superior warmth, breathability and moisture-wicking performance; spandex for stretch and ease of movement. - Self-fabric backing on collar with internal neck tape for comfort; locker loop for hang- drying. - Offset shoulder seams eliminate chafing under pack straps. - Long center-front zipper vents body heat and is backed by kissing welts for low-bulk comfort next to skin. - Full underarm gusset for range of motion and chafe-free comfort. - Elastic thumb loops for secure hand coverage. - Flatlock seams to minimize chafing; drop tail for increased coverage.