SPECIFICATIONS GABLE LOUVER GLFF1418WH-1/8 28 Gauge Galvanized Steel · N.F.V.: 110 sq. in. • 1/8 in. Screen • Rough Opening: 14 ¼ in. x 18 ¼ in. • Polyester Paint Finish 14 in. 35.56 cm 18 in. 45.