This is for an fully welded Dana 35 Differential Cover, welded inside and out. After they are welded the ring is machined flat to insure proper mounting surface to prevent leaks! 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! One of the reasons it is so hard to hurt is that we manufacture it out of A50 Plate Steel (US Steel), thats 50,000 PSI Tensile strength. All of our Diff Covers have countersink holes as a option so that if you do need to remove your cover the hardware will not me damaged. All finished covers come with a lifetime guarantee, no questions asked. All welds are made by a Competant, Certified Welder in the US from US manufactured Steel. If you are looking for unbrakeable ring gear and differental protection you have found it! This Diff Cover is Bullet Proof!