This is the upgraded hardware kit included with our 4.00 axle housing for the 3rd member. We use stronger and higher quality custom ARP studs that thread into our machined faceplate that are shouldered in the case area for higher horsepower applications. These also have a special chamfer on them that registers into our face plate to lock them in straight and reduces shear loads on the threads. The 3/8-16 side threads into our faceplates. These can also be used in our 3.50 housings as an upgrade. We don't use gaskets between the housing and the 3rd member, we use and recommend using a hi-temp silicon gasket maker like "the Right Stuff".