A waffle grid fleece interior holds warm air against the skin on the Le Bent Heavyweight Grid Fleece 1/4-Zip Top, while open channels vent moisture and excess heat when the effort picks up. This base layer top layers through changing seasons or stands alone when temperatures cool. What Our Gearhead(R) Experts Are Saying:"Cold climbs heat me up fast, and opening the quarter zip let the heat out while the grid interior kept the rest of the layer comfortable. At the top I zipped it back up and the warmth was still there."