Tungsten Carbide Boss Rounded Brushed Center Groove RingBOSS Tungsten Carbide Ring with Domed Center Groove and Brush Finish 6mm and 8mm This traditional 6 mm or 8 mm wide Tungsten Carbide Ring has a domed brush finished surface and a highly polished groove around the center of the ring, which provides a beautiful contrast. This elegant design, once reserved for platinum is now available in Tungsten.