ITW TEKS SELF-DRILLING SCREW, HEX HEAD, 21358, #14 X 2-1/2" THESE SCREWS ARE GREAT FOR USE IN HVAC AND ELECTRICAL APPLICATIONS. THESE SCREWS TAP THEIR OWN THREADS AND DO NOT REQUIRE PREDRILLING. ENGINEERED DRILL POINT AND FLUTE (PILOT SECTION). INSTALL WITH A STANDARD SCREW AND A 3/8 IN. HEX DRIVE BIT (INSTALLATION MATERIALS ARE NOT INCLUDED). FEATURES: IDEAL FOR FASTENING 20 TO 12-GAUGE METAL TO METAL USE TO ATTACH DUCT WORK TO STEEL FRAMING IN HVAC APPLICATIONS USE TO ATTACH ACCESSORIES TO STEEL FRAMING IN ELECTRICAL APPLICATIONS CAN BE USED IN OVERHEAD STEEL DOORS, HINGES AND LATCHES STRONG HOLDING POWER NO PRE-DRILLING IS NECESSARY