Double ended drill bit used for drilling multiple rivet holes 4.1mm in diameter made from M2 steel coated in Titanium Nitride 2 pack. TUSK HSS METAL DRILL BITS are constructed of M2 High Speed Steel for the best combination of strength, heat resistance and wear resistance. Great general purpose drill bits to suit a builder, electrician, plumber or DIV handyman to deal with timber, aluminium or steel.