PetSafe Passport Selective Entry and Selective Exit Pet Door, White, Small+ Advanced selective entry and exit technology lets you choose which pet can come and go and when; Offers multiple access options including Timer Mode to shedule access at specific times of day Pet wears included Passport Key on collar which sends a unique signal to door to operate as programmed for that pet; Program up to 20 Passport Keys for additional pets (sold separately) Energy efficient with U-flap system design and weather sealing gaskets; Multi-point locking flap system provides increased push-through resistance of 100 lbs. Easy programming using the LCD screen and 5-Button Navigation or using the included USB cable to connect to your computer; Uses a power adapter (included) For installation in exterior or interior people doors 1" to 2" thick with detailed instructions, cutting template and hardware included; Easily install in a Wall with the Passport Wall Kit (sold separately) For Small pets 25 lbs. or less; flap opening size is 7 1/8" W x 8 1/4" H Call, chat or email with our expert US-based customer care specialists six days a week; they are waiting to assist you and your pet with your product needs PetSafe Brand is an industry leading US manufacturer of pet behavior, containment, and lifestyle products since 1991, helping millions of people and pets each year