Constructed of M-35, 5% Cobalt Alloy Steel, high speed steel for super abrasive resistance and faster cutting than M2 in tough metals, the IRWIN® Cobalt Alloy Steel Metal Index Drill Bit Set features 135 split point tips that start on contact and cut with less force. Reduced shanks above 3/8" allow you to use the larger drill bits in a standard 3/8" chuck. The included case has removable cartridges to carry bits from case to worksite safely.