Wise 8WP21-374 - 12" to 18" Adjustable Height Pedestal with Slide Features Wide Height Adjustment and Fore and Aft Travel. Both of these Features are the only Way Boat ! 2 7/8" Diameter Thick Wall Post with 9" Diameter Base Plate with Recessed Mounting Holes. Seat Slide is Extruded Aluminum and Allows 5" of Fore and Aft Travel. Constructed of Extruded and Cast Polished Aluminum. Cast Aluminum Seat Mount Locks and Swivels 360 Degrees with Adjustment Knob. Simply Pull and Turn the Height Adjustment Knob to Raise or Lower your Seat. BIA Standard 4 Bolt Hole Pattern fits Virtually all Seat Brands.