The Patagonia Capilene 4 Pro Bottoms are our warmest and most breathable baselayer bottoms. Combining two exceptional technical fabrics to create hybrid warmth zones, the thighs and waist are made of Capilene Polartec Power Dry High Efficiency fabric) for superior warmth, breathability and moisture management, while knees, hips and seat use R1 fleece panels (6.8-oz Polartec Power Dry fabric) for additional warmth. Soft, stretchy and compressible, this piece features a smooth jersey face that glides beneath layers, a brushed-fleece interior that's soft next to skin and Polygiene permanent odor control. Other details include a gusseted crotch for mobility and an upper-calf length for a low-bulk fit with ski and snowboard boots.