The 506CU cutting wheel features a super abrasive grit called cubic boron nitride or CBN. CBN used on a cut-off wheel allows the wheel to remain sharp longer, stay cool, and it won’t shrink. The 506CU cutting wheel lasts at least 20 times longer than our fiberglass-reinforced cutting wheels based on internal testing. In. addition, with the Dremel premium metal cutting wheel you will spend less time changing wheels, save space storing replacement wheels and save money buying replacement wheels. For use with the 402 mandrel with screw.