O-Rings (bag of 100) tattoo machine spares.
Tattoo O-Rings are an important item to have on hand in every shop. They are used to minimize the vibration of the machine and give it a smoother run.
The O-Ring functions best when it is placed tightly under the spring and pulled back over the cap screw. An O-Ring can break at anytime, so make sure to have some stocked from C&S at your station.