Fits many models Keeps drive chain taunt For 10 mm diameter axles Replaces Currie SD-250-10 This steel chain tensioner controls the placement of your rear axle to the frame of the scooter Varying this distance adjusts the tension on the scooter drive chain This steel chain tensioner controls the placement of your rear axle to the frame of the scooter. Varying this distance adjusts the tension on the scooter drive chain. Common on many models of electric and gas mini bikes scooters without a spring loaded chain tension mechanism, including models from EVO, eZip, and Motovox. Fits 10 mm diameter axles, the most common size of rear axles used on gas and electric scooters and mini bikes. This scooter part is small, but it plays a big role in keeping your scooter moving. Hole Diameter: 11 mm Threaded Shaft Length: 29 mm