The old Cragar flat washers were hardened. The new stuff is not. Plus it's probably the cheapest Chinesium-metal they can get. As I mentioned previously, McGard at one time had the correct nuts with nice hardened washers. Not shown in their current on-line catalog, but I'd call them about it anyway. Or possibly try Gorilla Automotive.
By the way, nobody makes off-the-shelf washers that are the correct size for these nuts. I looked at every SAE, metric, aircraft, military, washer in existence and nobody has anything close.
