Heller hss co cobalt twist drills din 338 rn heller 17735 1 this set from heller includes 6 hss co cobalt twist drills equipped to tackle the toughest drilling jobs in stainless steel and metal they are made from a special hss steel with a 5 cobalt content this set includes drills ranging in diameter from 2mm to 8mm heller 17735 1 0990 hss co cobalt twist drills din 338 rn set 234568mm