Dressing in layers is a wise choice when you can't quite pin down the conditions you're going to face. That's pretty much true for all sports requiring technical clothing, but it's especially true of cycling, where a few thousand feet of elevation gain can land you in a completely different climate. The Gore Bike Wear WS Sleeveless Base Layer provides next-to-skin comfort and the wind-chill protection of WINDSTOPPER fabric no matter what you decide to wear on top of it.Keeping wind from infiltrating the space between your clothing and your skin is a necessity for staying warm, so the WINDSTOPPER membrane in this 100-percent polyester base layer covers your critical organs up front and also wraps around your sides/kidney area. Friction is kept to a minimum by flatlock seams that glide over your skin. The back is extra-long to cover your whole lumbar region, even when you're in the drops. As a nice touch, Gore Bike Wear made the front logo at the base of the neck reflective for added visibility when your jersey is unzipped. The Gore Bike Wear WS Sleeveless Base Layer is tight-fitting and comes in sizes Small through XX-Large. You can choose Black or White.