These are Surgical Steel Replacement Balls for Screwball Rings.
As with all of our Replacement Balls, due to different companies threading, we do not guarantee that they will fit the piece that you are ordering it for, even if it was originally purchased from us. These have the threaded post, and thus can only be used on the standard internally threaded Screwball Ring.

These are not to be used with Barbells, those you can find elsewhere in our catalog.
Also the size listing is for the size of the ring that you want the Replacement Ball for, Not The Ball Size.