Decorative Grille, Vent Cover, or Return Register. Made of Urethane Resin to fit over a 18"x18" duct or opening. Total size of vent is 20&rdquo;x20"x3/8", for wall and ceiling grilles (not for floor use). Incredible three dimensional detail of grille (see expanded view), not just hole punched sheet metal. Our urethane resin cast grilles are equal in surface quality to Investment casting or lost wax casting quality at a fraction of the cost. Much superior to the rough and grainy looking surfaces of cast iron or cast aluminum grilles. Maintenance free, you should not have to re-finish, remove rust, corrosion or mold for life of our exterior grade urethane resin grilles. Can be used in damp or wet locations, like exteriors, bathrooms, kitchens and indoor swimming pools or the other rooms on the same HVAC system as the pool room. Frequently used to replace unattractive exhaust fan covers in bathrooms. Easy installation, Pre-drilled screw holes and all necessary hardware provided. Our grilles are flat on the back, with no protrusion that needs to fit into the duct-work. Just place over duct, level and screw in. See attached spec sheet with drawing, measurements, Material Technical Data on resin, plus Free Air Flow and other information. Our grilles will also reduce or eliminate the irritating high pitched noise problems often found with stamped steel louvered return grilles. Urethane resin grilles will not vibrate and make noise like metal grilles do. Use our grilles to replace noisy high pitched metal return grilles. Often used a decorative speaker covers in home theaters as well. Arts & Crafts Style Grille; historic reproduction of possibly the best looking grille ever made in USA, Circa 1870's Use to replace old louvered grilles for wall & ceiling only (not for floors). Meets U.S. Governments General Services Administration code #1501003S standards for Historic Preservation Guidelines, for grilles in historic buildings. Use these grilles in new homes that want the traditional look or historic homes that need to preserve their vintage character.