The additional device which is placed at the door where you wish for your pup to go out
LightWeight: 3.25oz (92grams)
Size: L3.75" x W 2.5" x D 1"
Battery Life: 6+ Days
Battery Type: Built in rechargeable Lithium Cell Polymer
Connection Type: Home Wifi
Device is suitable for dogs of all sizes
Free App Download: Compatible with Apple iOS 10.0 and higher. compatible with iPhone 5 or iPad 3 or later