The Century Drill & Tool 29-pc Pro Grade Cobalt Drill Pod Set, No. 26529, is made in the U.S.A from M42 steel with 8% cobalt. The cobalt drill bits are designed to cut through extremely hard metals, including stainless steel. They are heat resistant and must be used and operated in power units that have an rpm speed of 1,500 or more for maximum efficiency. Aerospace NAS 907-J specifications. The set includes 3/8" RS 1/16" to 1/2" by 64ths drills.