Replacement sprocket hub for RPM Dominator II axles. Please call to make sure this will fit your application. It is CNC machined from aircraft quality billet 6061 T-6 aluminum. The seal surface portion is made of heat-treated chromoly steel, which is nickel plated and unique to RPM. This steel surface is far superior to our competitor’s aluminum surface, which can become grooved by the seal’s abrasion with dirt and grit potentially contaminating the bearings and leading to premature bearing failure.