Twin round belt idler pulley made from fiberglass reinforced nylon. Uses 6203 bearing with a 17mm bore. Our twin idler normally fits two 5/16" round belts, and works with any round belt down to 1/16". It can be used with a 3/8" round belt tire in one groove and a 5/16" drive belt in the other groove. OD is 2.25", ID is 1.83", 1.01" width. See this page for more information about the twin idler.