This hardware kit includes everything you need to add or replace the core covers of your Extreme Weather Aluminum™Pet Door. These plastic core covers line the inside of your door or wall, helping bridge the gap between both frames of your dog or cat’s pet door. This replacement kit comes in 3 sizes to fit your small, medium, or large Extreme Weather Pet Door™. Your pet deserves the best. Trust PetSafe® to help keep your pet healthy, safe and happy.