15-piece Cobalt Set is made of M-42 8 percent cobalt, high-speed steel for super-abrasive resistance in tough metals. 135-degree split point reduces feed pressure for easier penetration without work hardening. Durable rubber-sided case offers added impact resistance. Sliding latch design provides added security. Set includes an Irwin Pro Set Case made of durable molded ABS resin so it can hold up to anything the job site throws at it. Case includes a full-length metal hinge pin for maximum durability and long life. Bit identification is simple with easy-to-read size markings.