Surgical Stainless Steel (6) 6mm Balls, These will fit mostly 14g externally threaded barbells like where the ball has a hole so you can screw on to the barbell. These will also fit mostly tongue barbell, nipple barbell and other piercings. These have 14g universal threaded so in most 12g, 10g, 8g, 6g and 4g externally threaded barbell these will fit.