Attwood Lock'N-Pin 3/4"  Adjustable Pro-Post Power Pedestal Boat Seat Pin Post With Mount SP-3204  Non-Threaded Adjustable from 24" to 30" 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