Heller prefix hss metal drill bits heller 27427 2 this prefix universal drill bit from heller is a reliable metal drill bit ideal for unalloyed steel and non ferrous metal this 9 x 81 x 125mm bit has a web thinned centre point for accurate bit positioning supplied singly heller 27427 2 0911 prefix hss metal drill bit 90 x 81 x 125mm