Shotgun beads come in several sizes and threads. One very common one for American made guns is 5/40 thread with a bead diameter of 1/8 inch. When I get one in for bead replacement, I check for thread size. If its a common one, no problem. If its something different, I will determine what size I can change it to and drill and tap for that size. Very easy to do and doesnt cost much if you already have the drill and tap to work with.