Product Description AUTO-DRILL bits are made of cobalt alloy tool steel R6M5K5 Cobalt 5%. The cobalt in the steel composition allows for hardness retention at high temperatures, which is especially important when drilling difficult-to-machine stainless steels. - They have high wear resistance. - The drill bits are sharpened with a cross-shaped tip at a 135° angle, which allows for drilling high-hardness metals. - Hardness is 64-67 HRC. - Packaged in an envelope with a hole for convenient storage. Using high wear-resistant and hard drill bits significantly saves time spent on drilling and simplifies the work for the auto mechanic several times.