Heavy Duty Coverage. Replaced stock cover on 9.5 ratio GM 3 rear diff. The original filler hole was grabbed AND removed and the poorly fitted gasket was leaking. Using a razor knife scraped off the gasket from an old gasket maker and fitted to OEM spec. Painted it orange to match the different farm truck trims. It's perfect and doesn't leak. Just fill the port to the brim and call it good!