This exotic Comfort Fit tungsten inlay ring style is made of jewelry grade tungsten carbide that contains no cobalt. The ring has polished beveled edges and has an inlay of beautiful laboratory grown blue/green opal. This beautiful style comes in 6 mm, 8 mm, and 10 mm, which is great for couples who prefer a matching set tungsten wedding bands. Tungsten Carbide is the newest and strongest metal to be used in jewelry, ideal for men and women who are tired of rings that scratch easily. Please note, inlay is made of a softer material than tungsten and can scratch. Truly Free Lifetime Sizing and Lifetime Warranty on all tungsten rings, no exchange|sizing fees, which are charged by other retailers.