Externally Threaded And Internally Threaded Stainless Steel Curved Barbell, 14 Ga
Gauge (Thickness): 14 (1.6mm) Ball size: 5/32" (4mm) Material: 316L surgical grade stainless steel Threading Type: Internally Threaded This item has one end that is internally threaded and the other end is externally threaded. So, one end has the ball screw into the barbell and the other end has the barbell screw into the ball.