12" x 12", Green, Square Grate, Made Of Structural Foam Polyolefin With UV Inhibitors, The Open Surface Area Is 50.76 SQIN With 66.50 GPM, Use With The 12" x 12" 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.