The PetSafe Electronic SmartDoor and Smart Key are great not only because they give your pet the freedom that they deserve without you having to constantly let them in or out. This electronic pet door is energy efficient because it has a weather resistant seal and the flap is insulated. The automatic dog door will unlock when your pet comes close to the door and it will quickly relock after the pet has entered or exited its flaps. The automatic feature will keep other unwanted animals out that would normally be able to get into your regular non-locking electronic pet door. PetSafe’s Electronic SmartDoor and SmartKey are warranted by the manufacture with at lifetime limited warranty. The SmartKey is not big and bulky so the smaller dogs can wear it also. This automatic dog door has 3 different modes of operation which are: locked, unlocked and automatic access. The locked mode on the electronic pet door will allow you to contain your pet within the house or keep them outside in the yard. The automatic access mode will only allow the pet that is wearing the SmartKey to enter or exit the door. The unlock mode allows any animals to be able to get in and out of the door without a SmartKey. The unlock mode is convenient to use if you have other pets staying at your home so they can get in and out also. The SmartDoor electronic dog doors allow up to 5 SmartKeys to be used with the one electronic pet door.