Outperform and outlast traditional standard pitch models. Bi-metal construction with teeth made from specially hardened type M3 high speed steel. The varying teeth height and gullet sizes result in much faster cutting and longer life. For wood; mild, tool and stainless steels; cast iron; brass and aluminum. 51 sizes from 9/16” (14mmRdigid - 9/16" 14mm Variable Pitch Hole Saws - 52755) to 6” (152mm).