Need an extra collar forbothdogs in your family? Youve come to the right place. The Wireless Pet Containment System Receiver Collar helps keepall your pups secure in your yard while theyre running aroundandnapping together in the sunshine. PetSafe Wireless Pet Containment System Add-A-Dog Extra Receiver Collar can be used to either add another dog to an existing Wireless Containment System or as a replacement collar. You can add an unlimited number of pets to your containment system as long as each pet has a compatible receiver collar.