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"). The ring is also .375. The fill plug is a generous 1" ID for easy fill and oil level check. One of the reasons it is so hard to hurt is that we manufacture it out of A50 Plate Steel, thats 50,000 PSI Tensile strength. This is for an unwelded Ford 8.8 Differential Diff cover kit, intended to be welded inside and out.