Improving on traditional heat-treating processes, these hole saws are made from hardened carbon and alloy and then subjected to a proprietary cryogenic (deep freeze) hardening process. The core is hardened by minimizing austenite (a soft metal) and creating martensite (a harder metal). As a result, the hole saws last up to 50% longer than others. An optimized tooth form gives you up to two times faster cutting and wide-angled offset slots give you easy plug access. Everybody knows that getting the plug out is the most frustrating part of drilling any hole.