The Burton Synthetic Midweight Base Layer Crew top uses Midweight 200 fabric that reacts to body temperature, wicking faster when the effort ramps up and holding warmth when it drops. DRYRIDE Ultrawick construction keeps that moisture moving quickly to the surface, so the same top works through a cold chairlift ride and a hard push up a bootpack without needing a swap. What Our Gearhead® Experts Are Saying:"I wore this from a cold morning lift line into a sweaty bootpack an hour later, and it never felt clammy or overheated either way. The fabric seemed to catch up with me each time the effort changed, instead of staying stuck in whatever temperature I started in."