This extra receiver collar can be used to add another dog or as a replacement collar to the Free to Roam Wireless Fence? Stay+Play Wireless FenceA(R) or the Wireless Pet Containment System. The Free to Roam receiver collar includes 5 levels of static correction plus tone only adjustable to your pet's temperament.Features: Ergonomic collar design provides added comfort for pets Operates with RFA-67D-11 battery module; expected battery life is between 1-2 months For dogs 5 pounds and up Fits neck sizes 6-28 inches Tone-only mode alerts your pet with a beep Add an unlimited number of pets with additional wireless receiver collars Waterproof and submersible Low-battery indicator Compatible with Free to Roam Wireless Fence? PetSafeA(R) Wireless Pet Containment System (PIF-300 system IF-100 transmitter) and Stay+Play Wireless FenceA(R) (PIF00-12917).