This listing is for a roof vent cap for use with RV's, trailers, or motorhomes. These are made with PVC, and UV stabilizers were added, so they won't fade easily. The base is 5-1/4" in diameter, and it's 3" tall with the top part installed. There are 6 screw holes at the base, 3 of which are also used to secure the top cap to the base. Please note that installation hardware is not included in this listing.