NDS 9"x9" Black Square Grate. Made of structural foam polyolefin with UV inhibitors, this grate has an open surface area of 39.50 Sq.In. with 51.75 gpm. It is used with the 9"x9" catch basin series and rated a class B load, recommended for medium duty pneumatic tire traffic, autos & light trucks at speeds less than 20 mph. It comes with a limited lifetime warranty.