Material Both the screw and the metal washer are made of carbon steel with zinc-plated surface, which is corrosion-resistant and anti-rust, not easy to damage. The black washer is made of EPDM, which is wear and oxidation resistant. Feature The EPDM rubber washer can prevent leaks, loosening and damage the contact surface, which is bonded to the metal washer forming a tight sealing when you tighten the self-drilling screw. Easy to use The self-drilling screws can be directly screwed into the metal or wood without pre-drilling, not easy to deform and slide when use, high strength, long service life. All you need to install them with a power drive tool. Wide Application The hex head metal roofing screws are typically used in metal-to-metal and metal-to-wood applications, most commonly on thin metals such as iron panel, steel plate, aluminum panel, also used in wood, plastic sheet, composite board, etc.