Wise 8WP23-15S 15" Fixed Height Pedestal is built Stout to withstand rough seas. 2 7/8" Diameter Thick Wall Post with 9" Diameter Base Plate with Recessed Mounting Holes. Constructed of Extruded and Cast Polished Aluminum. Cast Aluminum Seat Mount Locks and Swivels 360 Degrees with Adjustment Handle and Knob. BIA Standard 4 Bolt Hole Pattern fits Virtually all Seat Brands.