This NDS Standard Series Valve Box has a 13" x 20" body that is tapered and has a minimum wall thickness of 0.250". The body has a double wall at the top cover seat area with a minimum thickness of 0.250". The cover seat area has 16 structural support ribs on the underside of the seat, each with a minimum thickness of 0.250". The bottom of the body has a 0.500" flange. The 13" x 20" cover has an average thickness of 0.250". The valve box has a 3/8" brass nut for the bolt-down as a standard feature.