High polished black ceramic ring blank with flat outside edges. Black color throughout material, zirconium ceramic is a very hard and durable material, same material used in heat shields, bulletproof vest, etc. Hypo-allergenic as well with superior scratch resistance. Custom made center channel groove is perfect for adding your own inlay material like crushed opal. Size 4 available in 4mm width upon request. 10mm wide ring = 5mm wide inlay 8mm wide ring = 4mm wide inlay 6mm wide ring = 3mm wide inlay 4mm wide ring = 2mm wide inlay