This is our basic differential cover, we see it as the only one worth making. It is a 1 piece Plate steel cover bent 8 ways, way hard to hurt in .375 (3/8"). However, the ring on the D35 is 1/2", we had to make it thicker to make enough room for the thickness of the cover, it just happens to make it 30% stronger too! The fill plug is a generous 1.0" ID for easy fill and oil level check. This is arguably the strongest Diff Cover made for a Dana 35 axle and with the Super D35 kits you need this cover. We manufacture this and all of our covers out of A50 Plate Steel, thats 50,000 PSI Tensile strength. After welding the mounting surface is machined absolutely flat for a perfect fit! This is for a fully welded D35 Differential Cover, welded inside and out with fill plug.