This Lynx LED armband is waterproof and runs on standard batteries, which are included (2x CR2032). The red armband features an LED, with 2 light modes, which provides enhanced visibility in the dark while exercising. Features: Batteries included (2 x CR2032) 2 light modes Waterproof Specifications: Color: red, black Material: polyester Gender: unisex Closure: velcro Batteries: yes Size: onesize