Armskins SL are thinner and lighter than original Armskins. Using a special polyester filament called FYnesse Sta Cool , we've created a three-season Armskin that makes the decision to wear something over your arms even easier. Armskins SL stay in place, wick moisture and guard arms against the elements to make your rides and runs more comfortable. Armskins SL are quick to put on, take off and stow thanks to their easy stretch, low bulk and lightweight. Just like our socks, Armskins are built to last using the highest quality (branded) fibers and DeFeet USA craftsmanship. Content: 67% Sta Cool polyester, 28% Nylon, 5% Lycra . Sizing: Small/Medium - Under 5'9"& under 160LBs. Large/Extra Large - Over 5'9"& Over 160LBs. Form Fit - ArmSkins Cover Wrist To Upper Biceps.