Clean, contemporary, louver design. Corrosion-resistant, paintable ABS plastic. For 3" or 4" I.D. ventilation system. Requires 1341 collector box for 3" system, or 1342 for 4" system. Install with #8 fasteners. Sized for installation even on highly contoured decks. Measures 2-3/4" wide, 17-9/16" long, 11/16" high.