"This Phoenix 1/2in. Sleeve Bushing allows you to quickly and easily change the dia. of a 5/8in. bore down to 1/2in. Bore Diameter in. Converts 5/8 in. bore to 1/2 in. bore, Part Type Bushings, Product Style Sleeve bushing, Compatible With Idler pulleys, Material Type Steel. Sleeve style bushing Quickly and easily converts 5/8in. bore to 1/2in. bore"