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, 18 mm 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, 6 x 2.8 in Keyway, Steel