9" x 9", Green, Square Grate, Made Of Structural Foam Polyolefin With UV Inhibitors, Open Surface Area Is 39.50 SQIN With 51.75 GPM, Use With The 9" x 9" Catch Basin Series, It Is Rated A Class B Load, Which Is Recommended For Medium Duty Pneumatic Tire Traffic, Autos & Light Trucks At Speeds Less Than 20 MPH.