Plug this into the grip in the separately sold Mini 4WD Screw & Nut Driver Set PRO to tighten up 2mm cap screws. This bit is magnetic, is crafted in chrome molybdenum vanadium steel, and has the bit size laser engraved in it. Length: 20mm Bit size: 1.5mm hex For use on 2mm cap screws, and other screws with 1.5mm hex holes.