Synergy Manufacturing 8009-12 Jeep JK/WJ Dana 30/44 HD Ball Joint Set (2 Uppers, 2 Lowers) Designed to replace the factory ball joints that are prone to premature wear on lifted vehicles with large off-road tires. Fully greasable metal on metal design. Machined bearing housing made from sintered graphite, bronze, and 1045 steel for a strong, smooth, bearing surface. Ball joint stud made from 4140 steel with an induction heat treated bearing surface for smooth operation and maximum life. Ball joint boot is made from tear/wear resistant silicone polyurethane. Outperforms the factory ball joint assembly and includes all necessary hardware for installation.