The Century Drill & Tool 29-pc Cobalt Drill Pod Set, No. 26929, are made from M35 steel with 5 percent cobalt. They are designed to cut through hard metals, including stainless steel. The cobalt drill bits are extremely heat resistant and must be used and operated in power units that have an rpm speed of 1,500 or more for maximum efficiency. Set includes 1/16" to 1/2" by 64ths drills.