Wise 8WP23-374 12" Fixed Height Pedestal with Slide is built stout to withstand rough seas. 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 handle and knob. BIA standard 4 bolt hole pattern fits virtually all seat brands.