Add-Gear Thermal Base Layer Ski Base Layer Mountaineering Base Layer Thermal Inner (Unisex - Top + Bottom) The Unisex thermal inner set (Top + Bottom) are made for active sports in cold weather such as skiing, Himalayan trekking and climbing in cold weather. Using soft, warm merino jersey fabric, we've built them for movement, using a gusset for mobility and soft, brushed waistband. The fabric is warm yet breathable, and resists odor naturally, so the thermal set is great as a cold weather running clothing or skiing baselayer, and you can wear them several times between washing.