10-24 x 1 1/4 Phillips Wafer Self Drilling Screw Zinc Plated (T3) . Designed to attach plywood to metal. Meets F.I.P.-1000.7 for torsional strength and speed. Meets ASTM A510 for carbon steel manufacturing. Zinc plating meets ASTM B117 for salt spray corrosion. Manufactured to SAE J78 for dimensional specifications.