Specifications: Type: Chain tensioner Material: 6061 aluminum alloy Application: Folding bike at a speed Features: stable chain, exquisite workmanship, light weight, easy installation, high quality materials, durable, bicycle accessories Size: approx. 5.5 x 9.3 cm to 2.17 x 3.66 inch Properties: Exquisite craftsmanship, high precision CNC machining, anode paint, bearing shaft, can be used with various guide wheels, the guide wheel generally has 11 teeth, it can also be used 13 teeth. The floating pulley and spring can be adjusted to the best chain tension. Lightweight and easy to install, made of high quality aluminum alloy, durable. The front derailleur guide wheel is light, small and easy to install and use. Scope of delivery: 1*Chain tensioner