The Arc’Teryx Delta Jersey Zip is made of Polartec Thermal Pro high void grid. This fabric rapidly wicks away moisture away from the skin, while still being highly breathable, light and warm. The Arc’Teryx Delta Jersey Zip top will be great for cool fall days or as an underlayer on the even colder days. It is quite warm for its weight. Gusseted underarm for maximum freedom of movement. A trim athletic fit with tapered wrists and hips to reduce bulk. Zip neck allows for easy pull-on and quick venting.