8"W X 4"H [Duct Opening] Never Rust Plastic 2-Way-Vertical Air Supply Register - HVAC Vent Duct Grille - Off White [Outer Dimensions: 9.75"W X 5.75"H] Color_Red Oak Actual Filter Size – 15

Actual Filter Size – 15 3/4"w x 33 3/4" x 1"

The premium durable material guarantees that they will never rust or wear through

The first number in a grille size

Actual Filter Size – 31 3/4"w x 7 3/4" x 1"

8"W X 4"H [Duct Opening] Never Rust Plastic 2-Way-Vertical Air Supply Register - HVAC Vent Duct Grille - Off White [Outer Dimensions: 9.75"W X 5.75"H] Color_Red Oak Actual Filter Size – 15+ Product Details Size 8"w X 4"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 9. 75" width X 5. 75" height. Design Rigid gauge ABS plastic. Rigid gauge built for durability and long life in mind, but still light and handy. Powder coat finish. Smooth, scratch resistant, beautiful. Looks like new after years of use. Screws Included High Quality High quality ABS plastic will never rust, no sharp