Suncourt Flush Fit Register Booster quietly boosts heated or cooled air automatically to improve circulation and comfort. Our new improved "Smart Technology" works automatically with forced air systems without requiring a seasonal adjustment. It has 5 fan speeds with dual fans to pull extra air out of weak registers, boosting airflow up to 85%. It is a simple, energy efficient, and safe solution for rooms that are too hot or too cold. Fits a standard 4" X 10" register. Can be installed in floor or wall registers. (wall registers require optional wall kit) Assembled in the USA. 12 month limited warranty.