Attwood Lock'N-Pin 3/4"  Adjustable Power Pedestal Boat Seat Pin Post With Mount SP-3004 Non-Threaded Adjustable from 14" to 17" high, 1.77" diameter brushed aluminum boat seat extension post with non-threaded, steel pin Lock'N-Pin prevents unintentional detachment for seat mounts, posts and bases The 3/4" system gives you outstanding economical performance Great for adding seating to fishing, pontoon or cruising boats Lock'N-Pin products meet ABYC Standard