The Synergy heavy-duty ball joints are a serious step up in strength from originals. They are greasable and have a sintered-metal bushing design which is more robust than the factory ball joints, which actually have plastic in them. The originals wear quickly with 35s, and are prone to failure. For JKs with RCV axleshafts (such as ours), Synergy includes a low-profile needle-type grease fitting. Before installing the ball joints, remove the polyurethane boot and spring retainer.