8mm inner diameter chain roller pulley slider tensioner wheel guid for pit dirt mini bike atv. Premium quality materials of seamless thick aluminium bushing and brand new bearings, strong strength and long durability. Designed as a direct replacement for the OEM design Compatible with both Upper AND Lower chain on your bike This chain pulley roller slider is an necessity for wheel guide, which helps the driving system to function well Chains rely on chain rollers for support. Without a lower chain roller, the chain can wear into the frame, without an upper chain roller the chain can cut into the air box. Package Included: 1 x Chain Pulley Roller Slider 1x M8 chain screw 1x M8 washer