Features: Featuring simple installation and disassembly, it is more convenient to use.The function of this pedal assist sensor is to help extend cycling mileage with good accuracy. Extend battery life and improve vehicle cruising range. Avoid damage to the battery due to high current discharge This product is perfectly suitable for bike, electric bicycle, etc. According to the speed of the turn of the foot to identify the power, pedal up in the process of riding is more lightweight and electricity saving. Specification Size:Diameter of outer ring 6.5cm, diameter of inner ring 1.5cm Package Include:1Pcs * E-bike Assist Sensor Note: 1. Due to the different monitor and lighting effect, the actual color of the item may be slightly different from the color shown on the pictures. 2. Please allow 1-3cm error due to manual measurement. (1 inch = 2.54 cm) Thanks for your support :)