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, 2-1/2 in Bore Dia, 3-7/8 in Small End/4 in Large End Barrel Dia, 5-3/4 in Hub Dia, 4-5/8 in Bolt Circle, 5-3/8 in Flange Dia, 0.62 in Flange Thickness, 3 Bolt Holes, 3/8-16 x 1-3/4 in (Cap Screw)/5/16-18 x 5/16 in (Set Screw) Screw, For Use With: MST® Sprockets and HR1 Weld-On Hub, 2.88 in Overall Length, 5/8 x 5/16 in Keyway, Ductile Iron