This ring fits the NC3FXX / NC3MXX range of connectors. Unlike the NP3X series, you can replace these without unsoldering anything (just unscrew the barrel). It was forged in the fires of Mount Doom, and some say that it will bring unequalled power to whoever possesses it. So, it's a bargain.
Be careful not to put it on your finger, unless you want Ringwraiths showing up and interrupting your sound check.