These steel gem balls for 18g and 16g internally-threaded HD Body Line, body jewelry are available in 6 colors and 2 sizes, including 2.5mm, and 3mm. Each ball and its internal 0.9mm threaded post are made from a single piece of surgical stainless steel with a bezel-set gem inset in the ball. (Gem is not glued in.) You can use these replacement gem balls with any 18g or 16g internally-threaded HD Body Line body jewelry with a matching internal 0.9mm thread pattern. These gem balls for 18g and 16g internally-threaded body jewelry are sold individually (price per 1) and separately from our straight barbells, labret studs, and other internally-threaded body jewelry shafts.