Base layers are for cold weather, right Well, if the idea is to keep you warm, yes. However, a true baselayer keeps you warm by keeping you dry. It's this quality that makes base layers optimal for wear even on the hottest days. Pearl Izumi's Transfer Lite Sleeveless Base Layer is designed to keep you dry and cool with its form fit and ultra light fabric.The Transfer Lite was constructed from a unique knit fabric called Minerale. Its individual yarns have 15 times the surface area of ordinary polyester yarn. This means that it wicks sweat more rapidly. And to deliver proper wicking performance in warmer weather, this efficiency of transport is a must. Understand that the body hugging fit is important you want the base layer to act like a second skin, immediately moving moisture to the outer surface of the fabric for rapid evaporation. This keeps you more comfortable by not feeling wet and clammy. You'll find this especially nice if a cool breeze kicks up in an arroyo or during a long descent.The name of this fabric isn't just for show. Minerale weaves a concoction of bacteria killing minerals into the Transfer Lite Sleeveless Base Layer, so your cycling clothing won't retain the smell of your eau d'perspiration.If you're weighing the choice of whether to go with the Transfer Lite Sleeveless Base Layer or the Transfer Lite Short Sleeve Base Layer, the sleeveless design may be more comfortable as a first ply beneath several other upper body pieces, making it as useful in winter as summer. The Pearl Izumi Transfer Lite Sleeveless Base Layer comes in five sizes from Small to XX Large and is available in Black or White.