Heller prefix hss metal drill bits heller 27419 7 this prefix universal drill bit from heller is a reliable metal drill bit ideal for unalloyed steel and non ferrous metal this 4 x 43 x 75mm bit has a web thinned centre point for accurate bit positioning supplied in packs of 2 heller 27419 7 0911 prefix hss metal drill bit 40 x 43 x 75mm pack of 2