Acorn Sw-Mw2Lg Mw Scrw, 2", Lt gray 250#9 15 metal to wood screws are sealing self piercing tapping screws made from heat treated C1022 steel, case hardened for roofing and siding applications. A 1 4" across flats high hat hex washer head with assembled EPDM washer offers easy driving and conforms to the metal surface for a secure and long lasting seal. The twin lead type 17 point and hi lo threads offer faster drive time and greater resistance to pullout. All screws are 1,000 hour salt