The factory felts are just over 1/2" in diameter by 5/16" thick. You can buy the medium density felt in sheets from places like Hobby Lobby. However, the minimum order is about enough for three lifetimes. And you will need a good 1/2" Arch Punch to cut them out of the sheet. If you need to buy something else from Clausing, the part number is 557-097 or 557-047 (there is apparently some confusion about the number). If your machine doesn't have felts in the spindle oil cups, you should install them. The felt does NOT need to go down into the part of the cup that is pressed into the headstock casting. And do NOT use felt rod made for installing windows and purchased from McMaster. It is too hard and will take several days before any oil put on the top gets through to the bottom. While you are at it, if your machine has them and they are the originals, replace the way oilers and rubber way wipers. too. Part numbers are 547-004 (oiler, 4 req'd), 938-003 (wiper, 4 req'd), 641-055 (retainer, 2 req'd) and 641-056 (retainer, 2 req'd). The retaining screw is #10 x 3/4" pan head self tapping (type A), part number 118534. Retainers and screws are only needed if yours have been lost or damaged or if you machine is old enough not to have them.