The Hot Chillys La Montana Bottom earns a 10 out of 10 on Hot Chilly's own warmth scale, built from brushed, micro-denier polyester fleece for mountain-weight protection in extreme cold. Micro-Elite Chamois gusset zones add stretch exactly where the body moves most, so the heavyweight fleece doesn't restrict a stride or a bootpack. MTF moisture transfer fibers pull sweat away from the skin, and the fabric's odor-blocking properties are guaranteed to hold up for 20 to 30 washes. What Our Gearhead(R) Experts Are Saying:"I wore this under my shell for three straight days of subzero lift lines without once feeling the cold creep in, and by the third day it still didn't smell like I needed a fresh pair. The stretch panels meant I never felt restricted hiking out to the sidecountry either."