Comfort Fit Knife Edge Center Center Tungsten Ring (Lifetime Sizing Guaranty) Comfort Fit Ring with a Knife Edge Crafted with a Mirrored Polished Finish Sizes 5 to 8 Rings are 6 Millimeters Wide; Sizes 9 to 13 are 8 Millimeters Wide Four Times Stronger than Titanium, Second in Hardness Only to the Diamond Will Keep its Shine for a Lifetime, Resists Scratches, Nicks, Pitting and Corrosion Tungsten Carbide is Hypoallergenic; Contains No Cobalt; Proudly Made in America; Lifetime Sizing Guaranty