Nickel plated copper alloy. Outside diameter .625", inside diameter .375", thickness .020". Keeps those hex nuts from chewing into the pickguard, amp faceplate, etc. Essential part for guitar and amplifier restoration; fits the pots and jacks found on those great '50s-'60s guitars and amps exactly. Brand New. Please note that we offer another version of this part without three stamped lines on the face. This version has lines and is thus more appropriate for modern guitars and amps. The Switchcraft version can also be considered an upgraded replacement for Fender Part Number 0031153049.