The Merino Blend 200 RealFleece Descender 1/2-Zip uses icebreaker's RealFleece 200 construction, a soft, brushed merino wool built to manage moisture and dry quickly through high-intensity effort rather than just insulate at rest. An underarm panel in Cool-Lite eyelet mesh adds targeted ventilation exactly where heat builds up fastest during hard climbs or fast descents. Thumb loops, offset seams, and flatlock construction keep the fit secure and friction-free, while a hidden chest pocket and dipped hem round out a half-zip built to move. What Our Gearhead(R) Experts Are Saying:"I wore this on a steep switchback climb where I usually overheat in anything fleece, and the underarm mesh actually vented the heat instead of trapping it. I stayed dry enough to keep the zip up most of the way, which never happens in a normal midlayer."