Capilene Midweight Bottoms

Most base layer bottoms are too heavy to recommend for active mountaineering. Put them on for an approach and you are sweating through them before you hit the glacier. The Capilene Lightweight Bottoms solve that problem by being light enough to actually wear while moving hard, layering cleanly under climbing pants without adding meaningful bulk or heat. Guides have been running the same two pairs for eight-plus years without replacing them, which is about as strong an endorsement of durability as exists. On Denali, one guide puts them on at 17 Camp and does not take them off until back at 14, which speaks to how well they regulate across a wide range of output levels. They are also comfortable enough to sleep in on cold nights, and light enough to justify bringing even when you are not sure you will need them. One candid note from a guide with five-plus seasons on these: hanging belays in tight quarters require some personal reorganization. You will figure it out.