Heller hss co cobalt twist drills din 338 rn heller 21348 6 these 13mm hss co cobalt twist drills from heller are 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 sold in packs of 5 heller 21348 6 0990 hss co cobalt twist drills din 338 rn 130mm pack of 5