@Fallguyz I made mine out of the edge of a 1" nylon washer 1.5mm thick from the hardware store. I used a leather punch die in a drill to cut the outside diameter, and a 3mm bit for the center hole. Any drill bit that is close to 3mm+ will work. It can fit a little snug on the valve stem shaft, but shouldn't be sloppy loose. If you don't think you have a way to cut the outside diameter, a set of big nail clippers will clip down the outside diameter fairly round with a little bit of work, as this isn't the critical diameter.