Models - Chain tensioner for all versions of both the Razor Pocket Mod and the Razor Sport Mod More Models - Will also fit Dynacraft Hello Kitty City Cruiser kids electric scooter Includes - Tensioner spring and roller included Easy DIY - The chain is adjusted by adjusting the rear wheel. Loosen the axle. Slide the wheel forward to loosen the chain. To tighten the chain, the opposite would be necessary. Razor compatible part number - W15130640079 Chain tensioner for all versions of both the Razor Pocket Mod and the Razor Sport Mod electric scooters