Fitment: The heavy duty MX350 chain tensioner is compatible with Razor MX350 MX400 SX350 ZR350 Dirt Rocket Bike, and the RSF350 Sports E-Bike Durable & Sturdy Material: Our MX400 chain tensioner is made of high quality metal material, with the function of anti-compression deformation and wear-resistant, not easy to break, is strong and durable, and can be used for a long time Important Function: The chain tensioner is an important part of the operation of the drive system. Good chain tensioner work as an adjuster roller guide can help the chain not loose, or fall off, and reduce sprocket or chain wear. Our MX400 chain tensioner ensures a smooth ride for you and getting good riding experience Easy Installation and Replacement: Our chain tensioner for Razor MX350 comes with a wrench, without complex tools and steps, you can complete the installation within a few minutes. Package Included: 1pc silver chain tensioner kit,1pc wrench, 10pc master link The heavy duty dirt bike chain tensioner is compatible with Razor MX350 MX400 SX350 ZR350 Dirt Rocket Bike, and the RSF350 Sports E-Bike