I removed the cassette on my bike for the first time last night and whoever put the lockring on really torqued it down, thank god I just bought a set of the vice whip pliers or I would have never got it off.
Anyway, the lockring crush washer was smashed and broken in two pieces. I have a new washer for a 12t lockring, it fits properly around the threads but overhangs the lockring by about 1mm. Do you think I could use it? Is it even necessary?