??Prevent Throwing Over the Chain??Chain Roller has a bearing at the core for smoother operation??Having the tensioner made a big difference. With the addition of this, it will prevent throwing over the chain??Inside Size??Inside diameter width 0.66 inch, please make sure whether the width of the chain can be used or what kind of chain you can prepare in advance before purchasing??compatible with????Fits for Most Motorized Bicycle Bike Pit Dirt Bike ATV Quad And Most Chinese Import Pit Bikes.??Package includes??:1 x Red 10mm chain roller.1 x Red 8mm chain roller .??Service Purpose??tisfy every customer, is our brand service purpose??If you have any problems or dissatisfaction after receiving the products, please contact us directly to get New Replacement or Return.