The PetSafe PIG00-10777 Stubborn Dog In-Ground Radio Fence is specifically designed for stubborn dogs that continually challenge the containment barrier. It has many features that make safe yet effective. The dog receives a warning tone as it approaches the barrier. Once in the barrier, the collar has four levels of progessive correction to stop it from leaving the containment zone. The collar also vibrates with each correction as an additional correction. The anti-linger feature ensures that your dog doesn't stay in the correction zone and run down the battery. The collar is waterproof and has a low battery indicator so you know exactly when you need to change batteries. It uses a standard 9 volt battery. It comes with both short and long contact points so it is effective on dogs with long or thick hair. The transmitter will cover an area up to 25 acres. Only the receiver can activate the collar which eliminates false correcttions from televisions, cordless phones, garage door openeners and other radio frequency equipment. To keep your dog from being over-corrected, the receiver will shut down if your dog remains in the barrier for over 20 seconds. It has a wire break alarm and built in lightning protection. For lightning prone areas, you can purchase additional lightning protection (found at the right under related products). PetSafe PIG00-10777 Stubborn Dog In-Ground Radio Fence includes: Transmitter One PRF-275-19 Collar (9 volt battery included) 500 feet of 20 gauge boundary wire 50 Boundary flags Long and short contact points Instuctional manual & DVD PetSafe PIG00-10777 Stubborn Dog In-Ground Radio Fence features: The 500 feet of boundary wire will cover approximately 1/4 acre. It can be expanded to cover up to 25 acres by purchasing additional wire Designed for stubborn or large dogs (must have at least 6" neck) Four progessive levels of correction, plus tone Vibration on correction Anti-linger protection to keep your pet from running down the batteries Fail-safe after 20 seconds on the transmitter to prevent over correction Wire break alarm Built in lightning protection Lifetime Limited Warranty Collar Dimensions Receiver length: 2.5 inches Receiver height: 1.5 inches Receiver width: 1.5 inches Collar and receiver weight: 6.5 ounces