This chain adjuster can change multi-speed bikes into single speed bike. The flywheel made of highly resistant stainless steel, hardness of 18 degrees. The screws made of stainless steel, anti corrosion and anti rust. The compression piece and gasket are made of 6061 aluminum alloy, CNC cutting, smooth surface and hollow design. Ensures perfect tension for your chain to make you pedal with less efforts, suitable for long time outdoor riding. This flywheel is compatible with 7-10 speed cassette flywheel, please choose 7-10 chain to install. Lightweight and mini, easy to install and use. Installation skills: the angle between the chain presser and the lower forklift frame 45 degrees to maximize the pulling force. Specification: Material: Aluminum Alloy Flywheel: 13T/14T/15T/16T/17T Size Chart: Chain Tensioner Length: 98.3mm/3.87inch Package Includes: 5 Pieces Tower Base Gaskets 1 Piece Flywheel Cover 1 Piece Flywheel 1 Piece Bike Chain Tensioner 2 Pieces Wrenches 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 on-line shopping!