Tungsten Ring with Carbon Fibre TUR21 Tungsten Ring with Carbon Fibre has a shank width of 8 mm. This ring is a Comfort Fit, making it a pleasure to wear. Tungsten Carbide is a very hard, dense metal, twice as hard as steel. It always remains polished and is scratch resistant. Available from ring sizes 5 to 15. Rings are supplied in a black ring box with white pad. The ring boxes are supplied in a sleeve, labeled with a product number and suggested retail price, for your convenience.