Materials: Hypoallergenic 100% 316L surgical steel externally threaded barbell and ball top with a bezel set genuine, natural stone cabochon. Bar Curve Length: Choose between 5/16" (8mm) or 3/8" (10mm). The standard / most common length used for belly piercings is 3/8" (10mm). If you are not sure what length you need for your piercing, please refer to the 'How to Measure a Curved Barbell' photo in this listing. Please note that all natural stones are uniquely one-of-a-kind, so the stones you receive may differ slightly from the photos. Our bezel set natural stone barbells are secured using non-toxic jewelry adhesive. In order to keep the stone intact, please do *not* boil your barbell, or soak it in any alcohol-based cleaners or any other highly acidic cleaning agents to sanitize it. Doing so may soften the adhesive and cause the stone to become dislodged. Instead, please sanitize your barbell using *only* warm water and antibacterial soap prior to inserting it into your piercing.