7/8"(21mm) x 1/8"(3mm) (5) JSP Heatless Wheels Heatless Original Wheels (grey) are made of a silicone carbide abrasive to make a unique, non-loading binder for rapid reduction through the final shaping of non-precious, semi-precious, precious alloys, porcelain, acrylic, denture teeth and natural dentition, without generating excessive heat. These wheels come in 15 different sizes and in regular grit. They also withstand a maximum of 20,000 rpm..Mizzy Features:– Made of silicone carbide 50/Pkg