Security Boss SB72 Heavy Duty Insulated Door Mount Dog DoorThe SB72 is a more durable, rugged version of the popular MaxSeal pet doors by Security Boss. They are the best sealing and insulating doors on the market, as well as the most secure when locked. These are the best pet doors by design. Only the finest materials are use in the manufacture of these doors by Security Boss Manufacturing LLC. The SB72 is designed to be maintained forever. This is the last pet door you will need to purchase for your dog.