U-Joints are cold forged from SCM-415 steel, precision ground journals are case hardened to HRC58-61. U Joints are pre-greased with hi-temp Lithium. Complex 3 grease Bearing cups feature a Quad lip seal to keep contamination out and grease in. Centrally located grease zerk and grease channels in bearing cup evenly distributes grease. Kits include cap plug to eliminate grease zerk for low clearance applications.