HVAC Premium has been providing superior in quality service for many many years. Our products are second to none, and we’ve help numerous contractors, DIY projects, and home improvement & remodeling specialist complete their masterpiece. If you are looking for a top of the line unit to enhance your project look no further than HVAC Premium HVAC Premium has sold over 5,000,000 Grilles - We are proud of our many happy customers! 12" X 4" Is The Size For The Duct Opening (floor/vent hole) Measurement Only, Actual Front End Outer Dimensions Are 13.5" X 5.5" - SEE BELOW IN DESCRIPTION HOW TO MEASURE A GRILLE SEE BELOW IN DESCRIPTION HOW TO MEASURE A FLOOR REGISTER High Quality - Our high quality rigid steel is the longest lasting grille on the market. The rigid steel will keep its shape as in brand new condition. Rigid Design - Noise Free Components - No Vibrating Louvers Etc. Easy Unrestricted Air Flow For Your Home HVAC System This Modern Victorian Floor Register Grille will provide your home with ideal and quiet, rattle free airflow for your air- conditioning and heating system as well as smooth opening and closing back dampers. How To Measure A Floor Register Overall Size: Measure the size of the opening. If your opening is 14" tall by 20" wide, order a 14 x 20. Height vs Width: The first number in a floor register size, represents the height, the second number represents the width. Example: If your opening is 14" tall by 20" wide, order a 14 x 20.