When a foot-wide ledge becomes your bed for the night, this compressible zip-neck helps turn up the heat. The micro-grid fleece interior of Patagonia's Capilene® Thermal Weight provides the greatest warmth combined with the greatest breathability of any baselayer in their lineup. Soft, stretchy and compressible, the Polartec® Power Grid™ fabric has a smooth face that glides beneath layers and a brushed fleece interior to warm your core, wick moisture and feel smooth against your skin. Capilene® Thermal Weight has 30-92% recycled content and is treated with Polygiene® permanent odor control. Features include a long center-front zipper for venting, full underarm gussets for unhindered shoulder mobility, elastic thumb loops for secure hand coverage, flatlock seams to minimize chafing, offset shoulder and side seams to lie smoothly beneath pack straps, and a drop tail for additional coverage.