Nickel plated steel. These thimbles press fit into the two holes bored into the face of your Mustang, Jazzmaster, Jaguar and Bass VI. Great for restoring older Jazzmasters, Jaguars etc. or for replacement use in USA Vintage Series instruments. I checked the reissue thimble against a '60s original and they are very close. On the latest (6/17/2022) version of this part I measured .493" across the upper lip, .3.73" barrel outside diameter, .309" inside diameter and .885" overall length. Brand New. Genuine Fender 0054447049. UPC 717669613327.