Same great seat with modified fittings to fit on DRE Gunnison, DRE Light Duty and NRS frames. Five sizes available: 17.5″ / 18.5″ / 19.5″ / 20.5″ / 21.5″ Measure inside to inside bay opening Chair legs will arc inward as they rise, so consider sizing up so that the chair will still function as a flip seat over your cooler or dry box. For example: If your cooler is 17″ wide, you should consider ordering the 18.5″ captain’s chair so that the chair legs are sure to clear the corner of the cooler. All hardware for mounting your Captain’s Chair is included. If your frame is more than 1.25″ in diameter please call us for a special order, we can do it!