Expand your In-Ground Fence™ boundary. Each spool of Extra In-Ground Boundary Wire comes with 500 ft. / 150 meters of 20 gauge, solid core, copper wire rated for direct burial. This covers up to 1/3 acre per spool. The length of wire needed will vary due to amount of twisted wire and the layout you select. A waterproof connection is needed for proper performance when adding additional boundary wire. We recommend using our Splice Kits (RFA-366) which include wire connectors and gel-filled capsules. Trust PetSafe® to help keep your pet healthy, safe and happy.How much wire do I need for an in-ground fence?