Wise 8WD562 Ladderback Helm Chair & Pedestal Combo Features 8WP21-374 ABYC Class AD Driver 12" to18" Adjustable Pedestal. Chair is constructed with thick wall rotational molded plastic frame with pre-mounted plastic injection molded mounting plate with T-Nut inserts. Aluminum back support brackets. Snap on and off cushions have high compression foam padding with mesh underlay to expel moisture. UV and mildew treated marine grade vinyl with embossed vinyl surface. Padded aluminum arm rests. Pedestal features polished cast aluminum 9" base plate with recessed knurled mounting holes. 2 7/8" diameter thick wall extruded aluminum post. Cast aluminum seat mount swivels 360 degrees and locks down tight.