This extra Receiver Collar can be used to add another dog or as a replacement collar to the Little Dog In-Ground Fence? System (PIG20-11041) or any PetSafe® In-Ground Fence? System. With a collar for neck sizes 15 cm – 66 cm (6″ – 26″), it is specially designed for your little dog. Our smallest waterproof collar is designed specifically for comfort. The reflective strip on the collar helps you find your small dog at night, so outside playtime doesn’t have to end when the sun goes down!