Need a solid foundation for your boat seat? Check out the Springfield Marine Square Pin-Type Base Plate. This 7-inch by 7-inch square plate is made from durable aluminum with a nice scratch-resistant satin finish. It's designed to accept standard 3/4-inch king pin-type seat posts or extensions (post not included). The plate has a plastic bushing that acts as a smooth bearing surface for the post to swivel on, and all the mounting holes are countersunk for a clean, flush installation with screws. To install it on your boat deck, you'll need to cut a 2.5-inch diameter hole. It's a simple, heavy-duty component that provides a secure and stable mount for your fishing seat, helm chair, or other marine seating. Made to handle the marine environment, it's a reliable part for your boat building or repair projects. Get your seat mounted right with this sturdy base plate.