Specifications Key Features: Bicycle Tail Light, Rear Lamp. Battery: 2 x CR2032 battery (not included). LEDs: 2 LEDs. Function: Waterproof. 4 Kinds of Switch: Full light, flash, slow flash, off. Button: One-Touch switch design, easy operation. Body Material: Flexible waterproof silicone Lit Time: All the sustainable use of light 35 hours Scintillation sustainable use of 160 hours. Body Color: Blue. Weight: 0.78oz. Dimension :3.62" x 1.18" x 1.18" (L x W x H). You can use it for: Outdoor activities, like biking / hiking