Our luxury wood vent covers are made of solid New Zealand Pine and are already primed so you can easily paint to match your walls or trim. Each vent includes a 3-inch (3") deep metal box that holds a 1" inch standard air filter and locks the vent cover in place with our patented design. HOW TO DETERMINE YOUR CORRECT SIZE: Remove your current metal return air vent. DO NOT measure your current metal return air vent; this will result in ordering the wrong size MEASURE YOUR HVAC INSIDE OPENING: Start by removing your old cover and 1" filter. Carefully measuring the inside duct width ( left to right) , then the height (up and down). Next, is your duct opening at least 1/8” larger than the size you plan to order? Example: a 20 W x 30 H requires a duct opening of 20 1/8 wide x 30 1/8 high. CHECK THE DEPTH OF YOUR OPENING: Make sure you have at least a 3-inch (3”) deep clearance inside the duct to house our 2-parts. ( Confirm by removing the metal or 1" filter) Review our sizes to select the one that fits: Sizes are listed by width first, then height (W x H) Choose your size width (W) Left to Right first, then height (H) Up and Down Order using width x height (W x H). EXAMPLE: a 20 wide x 25 high is a vertical vent with the louvers 20" in comparison, a 25 wide x 20 high is a horizontal orientation with the louvers 25" Confirm fit: Did you use the right orientation W x H? Is your opening 1/8” larger than the size you plan to order? For example, if you plan to order a 20 W x 30 H vent, your duct opening should be at least 20-1/8" W x 30-1/8" H AND 3” deep all the way around; Did you confirm 3" of depth clearance to install our 2-parts Our vents have a 2 inch wide outer wood frame, similar to a "picture frame" Make sure that there is enough space free from outside obstructions like baseboards, door jams or decorative trim. Place your order! HELPFUL HINTS: Orientation Matters! Our sizes go Width (W) x Height (H) The slats or louvers go the Width measurement ( left to right ). Call 713-660-0025; or email sales [!at] worthhp.com Our product comes with a 5-year warranty and you'll love the superior craftsmanship. Our Luxury AC vent covers look like custom millwork and will be a beautiful detail in your home. While 92% fit fast and easy, some wall modification might be needed for those with outliner HVAC applications. NOTE: To our local Houston customers, we offer Will Call Discounts.