Description:1. Material: Both the screw and the metal washer are made of carbon steel, a zinc-plated surface finish, which is corrosion-resistant; the black washer is made of EPDM, which is wear-resistant and oxidation-resistant.2. Advantages: The hex washer head has a flange with an EPDM rubber washer on the bottom to prevent leaks, loosening and damage to mating surfaces. The underside of the hex head provides a large flat bearing surface that reduces the possibility of crushing mating surfaces. When you tighten the screw, a flexible black EPDM rubber washer bonded to the metal washer creates a tight seal.3. Easy to use: Unlike self-tapping screws, these self-drilling screws drill a hole and tap a thread in one operation. All you need to install them with a power drive tool.4.
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