Bicycle Dynamo: The bicycle chain generator drives the gears to generate electricity and storage into lithium battery. Multi Purpose: It is easy to plug USB cable to charge. And this bicycle chain generator can also be a emergency light to ensure riding safety in the dark. Portable Usage: The bicycle dynamo stores energy by bicycle moving without wearing out bicycle chain and without energy leakage. High Quality Material: This bicycle dynamo is made of premium plastic, easy to install, very portable for biking travel. Wide Applications: The portable bicycle chain generator is widely suitable for outdoor bikes travel. Specification: Material: Plastic Size Chart: 9.9cmx6.2cm/3.9inchx2.44inch Package Includes: 1 Piece Bicycle Dynamo Note: 1. Please allow slightly error due to manual measurement. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. 3. Wish you a wonderful online shopping