BAUER™ Fractional, Number, and Letter Index Drill Bits are constructed from cobalt high-speed steel that lasts longer and cuts faster than standard high-speed steel bits. These bits retain their hardness up to 1000°F, making them great for drilling cast iron, heat-treated steel, stainless steel, and other hard materials. This full assortment of drill bits comes with an indexed metal storage case for easy size selection.