As outlined in older posts, I use 1/8" Duro Felt, and sharpen a .45 Colt or a .357 Mag case, (with a couple grooves, sort of forms two teeth on the end of the case) file off the rims, and chuck them in a drill. You can cut a thousand or so from a $12 roll. You will find more info if you do a search here. Wouldn't worry about measuring, they fit fine in .44 or .36 respectively. Then soak in your Gatofeo. Some of the older posters say the drill thing works a lot better than a punch.