If you’re installing a SmartDoor Connected Pet Door in metal, glass, or a wall, then you’ll need this SmartDoor Installation Adaptor. The adaptor minimizes the interference that may occur between a metal door, your Pet Door Key and the sensor that gives them access through the SmartDoor. This installation adaptor will help secure your new pet door in a safe manner by giving you something to screw into. Some installation locations require additional PetSafe® accessories or professional help. The installation adaptor comes in two sizes, Medium and Large, and must match the size of your existing SmartDoor. Please note that only the Medium SmartDoor can be installed in glass. Consult a glazier for glass installations. This installation adaptor is only compatible with the SmartDoor Connected Pet Door. Your pet deserves the best. Trust PetSafe® to keep your pet healthy, safe and happy.