The Replacement Safety Sensors project an invisible light beam across the inside of the garage door to prevent accidents and fit every Chamberlain® Garage Door Opener manufactured after 1997. Use the Replacement Safety Sensors to replace defective or damaged sensors and ensure peace of mind. Safety sensors are required for safe use of all Chamberlain Garage Door Openers. Whenever there is an obstruction the garage door will automatically reverse before causing damage. Includes one-year warranty mounting brackets and 18 of extension wire for easy installation.