Central bracket with square pin for 68 mm bike bottom Quick and easy installation without adjustment The integrated system can protect the frame higher powerit is better than the normal middle movement of the structure Fine workmanshipsmall dimensional error 2 bearing precision wire design which allows it to connect better to the bike arm SEAL BEARINGSealed cartridge bearing assembly maintenancefree sealed cartridge protects against dirt mud and water Good ServiceIf you have any problems with this product you can contact us at any time