GCR18 Round Cedar Wood Gable Vent ~ Louver box 17.5 x 17.5 ~ Overall 21.5" x 21.5" ~ Kimball Designs Sanded Smooth Functional Ventilation Knot free Clear kiln dried Western Red Cedar Mitred joints, Exterior grade glue Aluminum Bug and Rodent Screen Louver Box: 17.5" x 17.5" x 3" Overall including trim: 21.5" x 21.5" x 3.75"