Features and Benefits: Ice Hardened™ for up to 50% longer life than competition Optimized tooth form for up to 2 times faster cutting Functional slots for faster plug removal Matrix II bi-metal teeth for greater durability Milwaukee® Ice Hardened™ products utilize a proprietary cryogenic hardening process that improves upon traditional heat treat processes. Unlike surface coatings that wear away cryogenics harden to the core by minimizing soft metal (austenite) and creating more hard metal (martensite). The result is a product that is more consistently hard throughout resulting in life up to 50% longer than the competition. RPM mild steel: 210 RPM stainless steel: 105 RPM cast iron: 140 RPM aluminum: 315