"What Our Gearhead® Experts Are Saying:""This is my go-to base layer for mixed conditions—light enough for high-output days, but warm enough for early starts. I love the soft merino blend, and the half-zip is perfect for quick venting when I start to heat up.""We reach for the Outdoor Research Alpine Onset 1/2-Zip Top when early mornings demand a little extra warmth but we know the day will heat up. Made with a soft blend of non-mulesed merino wool, polyester, and Lycra, this layer delivers the breathable insulation we need for skiing, hiking, or climbing—without ever feeling bulky or restrictive. The merino blend naturally wicks moisture and resists odors, keeping us dry and comfortable from trailhead to summit. The thoughtful construction features like flat seams, raglan sleeves, and thumbholes dial in the fit, while the 1/2-zip front lets us dump heat on uphill pushes. Whether we're layering for stormy mountain days or chilly trail runs, the Alpine Onset 1/2-Zip is a staple in our kit."