MST® bushings are easy to install and remove. They are split through the barrel and have a taper to provide a true clamp on the shaft. They are keyed to both the shaft and the hub to help during \"blind\" installations. Martin MST Bushing, Standard, 1/2 in Bore Dia, 1.57 in Small End/1.625 in Large End Barrel Dia, 2-1/2 in Hub Dia, 2 in Bolt Circle, 2-1/2 in Flange Dia, 1/4 in Flange Thickness, 2 Bolt Holes, 1/4-20 x 3/4 in Screw, For Use With: MST® Sprockets and HH1/HCH1 Weld-On Hubs, 1-1/4 in Overall Length, 1/8 x 1/16 in Keyway, Steel