4" X 8" Or 8" X 4" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 5.75 X 9.75] Outdoor Vent Covers 5" Depth] - SEE PHOTOS

5" Depth] - SEE PHOTOS - Leveler

Measuring 6" in diameter for the duct opening

+ Product Details Size & Compatibility – The 6" Galvanized Sheet Metal 90 Degree Oval Vertical Angle Elbow is compatible with Duct 6"

12" x 4" Floor Register HVAC Air Supply Grille - Heavy Duty Rigid Built - Plastic Never Rust Vent Duct Cover

this fitting is perfectly compatible with 18-inch ducts

4" X 8" Or 8" X 4" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 5.75 X 9.75] Outdoor Vent Covers 5" Depth] - SEE PHOTOS+ Product Details Size 4"w X 8"h or 8" x 4" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 5. 75" width X 9. 75" height. High Quality High grade steel construction meant for high foot traffic areas. Installation Location Floor. Design Easy drop in installation. Powder Coat Finish Smooth, shiny, scratch resistant, with no sharp edges. Looks like it was just waxed. Quality Packaging Carefully