What Our Gearhead® Experts Are Saying: I didnt know I needed a one-piece baselayer until I tried the Coefficient LT. The Power Grid fleece hits the perfect balance of warmth and breathability on big approaches, and the under-helmet hood is clutch on pre-dawn starts. The zips are thoughtfully placed, so nature breaks arent a hassle. Its warm, light, and honestly the easiest layering system for cold alpine days. We pull on the Black Diamond Coefficient LT One-Piece when we want streamlined, head-to-toe warmth for cold alpine approaches and early-morning tours. Polartec Power Grid fleece brings lightweight insulation with impressive moisture management, helping us stay warm without overheating as we push into higher terrain. The wicking efficiency and breathability make this one-and-done baselayer feel reliable on everything from steep skin tracks to long bootpacks. Thoughtful details round out the design: a split back opening and front flap opening keep things simple when the mountain requires a pit stop, while the 3/4-length zipper lets us get in and out quickly at the trailhead. An under-helmet hood adds an extra layer of comfort when the wind picks up, and flatlock seams keep every movement chafe-free. For cold-weather missions that demand efficiency, this one-piece becomes our most dependable starting layer. Material: Polartec Light Weight Power Grid Fleece (90% Polyester, 10% Elastane, 119gsm) Fit: regular, one-piece Insulation Weight: migweight Style: one-piece, base layer Pockets: zippered chest