Arcteryx Delta Grid Zip T-Neck - Women's: Layer the Arc’teryx Delta AR Zip Neck Shirt over a baselayer, under a vest, under a jacket, or just wear it on its own. A high-loft fleece inner face provides exceptional insulation. This shirt packs down so small, you almost need a magnifying glass to find it in your pack. But pull it out, and voila—you have a handy warm layer to keep you comfy. With its clean trim look this a perfect baselayer that can provide warmth on the mountain and style on the town.