PetSafe Magnetic Key 4-Way Locking Cat Door, Exterior/Interior, White Selective entry cat door uses magnets to help keep strays and wild animals out of your home, while giving your cat access to come and go Includes a 4-Way, knob-style lock with 4 options to give you complete control of your cat's access: open, locked, in-only (cat can enter but not exit), and out-only (cat can exit but not enter) High-impact, white plastic frame with a transparent, hard flap that cats prefer for ease of use and a U-flap system to help keep weather and drafts out of your home For installation in interior or exterior people doors 1/16" to 2 1/8" thick; Installation in thicker doors or walls require the PetSafe Wall Tunnel Extension Tunnel for an extra 1 7/8" thickness (tunnels are stackable for any thickness); Detailed installation instructions, cutting template and hardware included For small cats or dogs 15 lbs. or less; flap opening size 6" W x 5 1/8" H Works with an unlimited number of keys with 1 Magnetic Key and 1 black adjustable cat collar included 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