This 16g (1.2mm) externally threaded circular barbell is available in 3 diameters, 5/16” (8mm) – 3/8″ (10 mm) & 7/16″ (12MM). Each ring is crafted from 316L ASTM F-138 Implant Grade Stainless Steel. 3mm. The balls thread onto the 1.2mm external threading found at each end of the barbell. These rings can be used for a variety of different piercings including: Earlobe – Tragus – Septum – Eyebrow.