A base layer is designed to be the piece of clothing closest to your skin and should keep warmth in and wick away sweat. Bow recommended a base layer made by a certain well-known upmarket cycling brand in the 'Ultimate Gear' roundup recently, as it turned out to be excellent for archery; adding confidence and support as well as cosiness, and flexing exceptionally well for shooting. As well as being easily washable, the other big plus to a base layer is the portability, they are a light and easily-squished addition to any outdoor kit.