Specifications: Type: Chain tensioner Material: 6061 aluminum alloy Application: Suitable for folding bikes at speed Features: stable chain, exquisite workmanship, lightweight, 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, anodized finish, bearing shaft, compatible with various guide wheels, generally 11 teeth but can also accommodate 13 teeth. The floating pulley and spring can be adjusted for optimal chain tension. Lightweight and easy to install, made of high quality aluminum alloy, durable. The front derailleur guide wheel is compact, lightweight, and simple to use. Scope of delivery: 1*Chain tensioner