This system is safe and effective for all hard-to-train pets. The PetSafe In-Ground Radio Fence has been proven safe, comfortable, and effective for hard-to-train pets over 8 pounds. The system works delivering mild static correction through two contacts points on a receiver collar your dog wears on his neck. You'll need to install an underground fence by burying the included boundary wire and flags. Your pet is allowed to freely roam within a safe area that you establish. If your pet crosses the established barrier, a correction will be sent to get your pet's attention, but will not harm him. The collar also features a tone plus vibration only mode for effective pet training. Features: Covers up to 10 acres with additional wire and flags* System includes enough boundary wire and flags to cover 13 acre Receiver designed for stubborn or hard to train pets Five progressive levels of correction Low battery indicator flashes when battery gets low Tone plus vibration only mode for training UltraLight Receiver with adjustable collar System includes: Transmitter w Power Adapter UltraLight Receiver with adjustable, waterproof collar (6.5-oz waterproof dog collar adjusts from 6 - 28) Wire Nuts Test Light Tool 9-Volt Alkaline Battery 20 Gauge Boundary Wire - 500 feet 50 Training Flags (enough for 13 acre Operating & Training Guide Other items you may need for installation: Additional boundary wire and flags (dependable upon perimeter), tape measure, small phillips screwdriver, drill and mounting hardware, shovel or lawn edger, pliers, wire stripping pliers, scissors, lighter, electrical tape, additional wire nuts, waterproofing compound (e.g. silicone caulk), PVC pipe or water hose, circular saw with masonry blade, patching compound, staple gun, non metallic collar and leash. Additional boundary wire: PetSafe recommends the use of 20 gauge insulated multi-strand copper wire for direct burial. The following indicates the approximate length of boundary wire needed for a rectangular, single-loop layout. Length will vary due to the amount of twisted wire and layout used. 14 Acre: 415 feet of wire needed 13 Acre: 480 feet of wire needed 12 Acre: 590 feet of wire needed 1 Acre: 835 feet of wire needed 2 Acres: 1180 feet of wire needed 5 Acres: 1870 feet of wire needed 10 Acres: 2800 feet of wire needed PetSafe Stubborn Dog In-Ground Fence