As others have said, this is an excellent muzzle device mounting solution - JP Enterprises Double Crush Washer

Considering a standard crush washer will run you $2 ea or more from OP, this is a great value. Not only does it look good, it's also quite concentric and provides a stronger mount than standard CW's. As others have suggested, these have enough room to be turned at least two full rotations, allowing them to be used twice. I HAVE in fact used the same one twice, after deciding I wanted a little more than a flash hider... it works!

It's a simple part that seems expensive for what it is, but is also one of those parts that, after having used the alternative enough times, I wouldn't bother with a regular crush washer again. Once you get your hands on one, you'll understand.

While I'm here, I'll give JP some more praise: try their $20 chrome silicon tuned and polished spring... also my new standard.

Happy building, ladies and gentleman.