Each of these 115 cobalt drill bits comes organized in a metal indexed storage case for easy transport to your worksite. These cobalt drill bits retain their hardness up to 1000 degrees Fahrenheit making them ideal for drilling cast iron, heat-treated steel, stainless steel and other hard materials. With aggressive 135 degree tips, these cobalt drills bits not only last longer but also cut faster than standard high speed steel bits. Cobalt steel bits last longer, cut faster than high speed steel. 29 fractional sizes: 1/16 in. 26 letter sizes: A-Z. 60 numbered wire gauges:1 to 60. Retains hardness at temperatures up to 1000° F.