Our Titanium is Nickel Free, half the weight of Steel, and available in several brilliant colors, without the use of dyes to color it. We only use G23TI Surgical Titanium or 6AI-4VEli Implantable Titanium. Both of these grades have been successfully used worldwide for heart valves, pacemakers, and implants. Circular Barbells are a great design for people who frequently remove or change their jewelry. All Internally Threaded, and can be worn with virtually any piercing. Circular Barbell's are measured using the inside diameter.