Compact and lightweight design makes it add no extra pressure to the bike and not take up too much space. Waterproof design makes it not easy to damage by rain to extend service life. Fastener tape design makes it easy to install without using other tool. It is constructed of plastics material. The length of the product is 5.5cm, the width is 3cm, the height is 1.8cm. It can be used for bike, backpack, helmet, arm and so on. Item Name: Bike Light Material: Plastics Battery: 2 x Button Batteries (Included) Features: Waterproof, Long Endurance, Compact Size Details: Size: 5.5cm x 3cm x 1.8cm/2.17" x 1.18" x 0.71" (Approx.) Notes: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 1 x Tail Light 1 x Charging Cable 1 x Fastener Tape