This is our set of 20 (1552020) which includes 1 each of numbers: 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, and 80 of the jobbers length twist drills made of the finest high-speed steel. Heat treated to a hardness of 63–65 HRC and precision-ground to a tolerance of +.0000 to –.0003". Can be used on all metals. Made in USA.  See also our set of 12 (1552010) which includes 1 each of drill numbers: 55, 57, 60, 62, 64, 65, 66, 68, 70, 72, 73, and 75 .