Highly recommended time saver! This machine tooled aluminum adapter will fit onto any angle grinder with a 5/8" x 11 tpi spindle. It allows wobble-free, high speed drilling and can reduce your log inoculation time dramatically. For use with our high speed 13mm, 12.5mm 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). PLEASE NOTE: If using a cordless angle grinder, recharge and change batteries often to avoid bit from becoming stuck in the log.