This internally threaded steel screw on jewelry appears to be a captive bead ring without all of the hassle. One end does not have a ball and the other end has an 8mm ball that screws into the circular shaft. This is a cross between a captive bead ring and a circular barbell. It can be used for a variety of piercings, try it out on your 8g piercing today. IN 3 DIAMETERS 13MM (1/2″) 16MM (5/8″) & 19MM (3/4″). Autoclave sterilized in a sealed pouch for your safety.