A rubber O-ring on these ASA plastic deck plates creates a watertight seal for safety. Screw-in style has a single-start, non-jamming (no cross-threading), extra-strong, self-cleaning buttress thread. Use only 100% silicone caulk. Material: ASA UV-resistant Plastic Fasteners: #8 pan head screw or thru-bolts (sold separately). Warranty: One year