Highly recommended time saver! This machine tooled steel adapter will fit into any angle grinder with an M14 spindle. It allows wobble-free high speed drilling and can reduce your log inoculation time dramatically. More durable and longer lasting than aluminum adapter option. For use with our high speed 13mm, 12mm or 8.5mm drill bits only (this adapter will NOT accept the 5/16" brad point drill bit or the 8.5mm and 12mm HEX shaft screw tip bits).