I have 4 Cragar SS Unilug rims mounted on a 5" Lincoln bolt-on (yes they were around in the late 70's). Aluminum "bumps" on the rim on either side of the lug hole. I had the original Cragar washers, but the chrome had come off and they were rusty. I didn't want Cragars again because they would rust again, it's stainless steel. They are flat. The Cragar washers I had were slightly hollow, like the Bellville washer. It was a little fun tightening the Cragar washers. Continue to tighten to flatten the washer until it is flat, then the torque is just right. The McGard washer, which is flat, turns straight up. Not a weird "I didn't rip that nut off" feeling ever experienced with Cragar washers.