Versatile mounting adapters simplify the job of assembly and help to reduce overall cost. Made of high quality sintered iron materials, they are press-fitted in place at the factory so that you need handle only one component, the \"finished\" belt idler assembly. There's no need to stock lots of separate components and deal with multiple suppliers. Simply order the mounting adapter(s) you need at the same time you order the belt pulley and they will be factory installed without charge. The three standard types are available in a choice of widths and bore sizes to meet most mounting requirements. However, our flexible tooling approach allows \"specials\" to be produced quickly and economically and frequently with little or no tooling charge. Brewer Universal Drive Tensioner Bore Adapter, 3/8 in Bore, For Use With: Model 6203 0.472 in W Standard Ball Bearing, Sintered Iron