With its contemporary design and advanced entry and exit technology, the Passport Pet Access Smart System™ provides freedom and peace of mind like no other pet door. Using radio-frequency identification (RFID) technology, the Passport™ reads the Passport Key™ worn on your pet’s collar. This allows only pets with programmed IDs to enter and exit the home, while keeping out other pets, wild animals, and strays. Up to 20 keys can be programmed to your door and you can set an optional audible alert to let you know when pets are entering or exiting the door. Choose from advanced selective entry and exit by pet, multiple access options (such as in-only access and out-only access), and access only at specific times of the day. Programming is easy using the LCD screen and 5-button navigation or by connecting to your computer with the included USB cable. A wireless connection allows for convenient future remote programming from any smart device, even when you're not at home (requires Passport Wireless Card). This Small door has a flap opening measuring 7 1/8 x 8 1/4 inches and is recommended for pets 1-25 pounds. Also available in a Medium option for larger pets. The Passport™ gives you complete control of each pet’s access.