When we bought our used 2005 Corvette, it already had McGard lock nuts installed with the socket in the glove box. In the fall I would put the original painted wheels on for winter storage so the wheels had been off and on the car a few times and I ALWAYS use a torque wrench, never trusting the Armstrong torque wrench. On removing the wheels one fall, a big chunk broke out of one of the lock nuts. Thinking that I may not have had the socket on straight, I was extra careful and a small piece broke off another. I managed to get the bad nut off with the help of my die grinder, hammer and chisel. The nuts were glass hard. 62 Rockwell or more I would think. I run without them now. The picture shows from left to right, the socket, a good nut, the nut with the small piece out of it and the bad one that took a lot of work to remove. I spent 41 years as a tool and die maker so am used to such stuff. The average person, without the proper equipment would have had to go to a dealer to get the work done.