This is a high quality waterproof inspection Deck plate made of UV stabilized plastic. Sleek design hiding the screwholes underneath the top plate. Deck plate tightens by hand twist.
Opening Diameter: 4"
Overall Diameter: 6"
Distance between two opposite screw holes: 5 1/4"
You will need to use silicone waterproof sealants on each of the six screw holes to prevent water from seeping through the holes.