What Our Gearhead(R) Experts Are Saying:"I wore this under my shell on a long backcountry tour where the temperature swung from freezing at the trailhead to sweaty on the skin track. The HeiQ Smart Temp tech actually kept me from overheating on the climb, and the hidden thumbholes kept my sleeves in place the whole day."Backcountry days rarely stay one temperature for long, and a base layer that can't keep up will leave you either freezing at the trailhead or soaked by the second climb. Burton's Synthetic Midweight Baselayer Crew Top solves that with body-heat-activated HeiQ Smart Temp technology working underneath a midweight peached jersey fabric, so your core temperature stays balanced whether you're skinning uphill or standing around at the summit. The slim fit sits close to the body without restricting movement, and four-way stretch fabrication lets you reach, twist, and stride without the fabric fighting back. Chafe-free softlock seams and double-needle stitching hold up to repeated layering, while hidden thumbholes keep sleeves anchored under gloves during long days on the mountain.