This page includes Aluminum Rear Seal Caps & Attaching Hardware. The rear seal cap holds the bottom half of the rear seal to the crank and provides a surface for the oil pan to seal up against. As a tech tip, if you are having problems with rear main seal leaks, have your machine shop surface a small amount of material (approx. .010") off the bottom of the rear seal cap using their Rod/Main cap cutter. This will hold the seal more tightly against the crank and solve many leak problems.