The Burton Lightweight Base Layer Pant strips down to the thinnest build in the lineup without giving up warmth, thanks to HeiQ Smart Temp regulating heat through changing effort. A next-to-skin fit with four-way stretch keeps the thin fabric out of the way, so it layers under a shell pant without adding any bulk of its own. What Our Gearhead® Experts Are Saying:"I wore these on a cold morning tour expecting to need a heavier layer by the second climb, and HeiQ Smart Temp kept me warm through the whole push without ever feeling clammy. The fabric is thin enough that I forgot I had a base layer on at all."