Arm cover knitted with seamless WHOLEGARMENT (R). The arms are woven from 100% cotton, and the hands and fingers, which tend to get stuffy with sweat, are made of a silk blend that feels smooth against the skin. While covering the upper arm, back of the hand, and thumb, you can still use your fingertips, so you can operate your smartphone and open and close the key smoothly. It's thin, so it's light and comfortable to wear. It is also recommended during good night.