The Basis PeakWool Mid Tight is a merino wool base layer built for aerobic effort in cold conditions, cut with a front fly and gusset for a full range of motion. Its PeakWool(TM) fabric blends RWS-certified merino, TENCEL, recycled nylon, and spandex into a midweight, four-way stretch construction that moves through a stride or a skin track without binding. Flatlock seams and a brushed elastic waistband keep the fit close and chafe-free under a shell. What Our Gearhead(R) Experts Are Saying:"I've worn heavier tights that fought me on the way up a skin track. This one stretches through every stride instead of stacking up at the knee, so I forget I'm wearing a base layer at all."