What Our Gearhead(R) Experts Are Saying:"I wore these under my shell on a windy trail run when the temperature dropped fast. The four-way stretch never restricted my stride, and the activated carbon fabric kept things odor-free through a sweaty climb and the descent after."A cold start to a trail run, breath visible in the air, calls for a base layer that disappears the moment you start moving. The Clima-Tek Bottom from Hot Chillys does exactly that, a soft spun polyester and spandex blend that moves with every stride instead of fighting against it, built to layer under a shell or stand alone once the sun climbs higher. Moisture transfer fibers pull sweat away from skin as effort increases, while activated carbon woven into the fabric manages both temperature and odor across long days out. A covered waistband with drawstring keeps things secure through technical movement, and side pockets with a hidden interior key pocket mean no need for a pack on shorter missions.