Our Fence Charger Lightning Fuse 4J< is designed to protect against Lightning Strikes to your fence on the Hot or Ground fence. When lightning strikes your fence the 4J< Fuse will blow and not your charger. The 4J< Fuse is designed for the smaller Fence Chargers that are 4-Joule or less. They are designed to carry the full load from the fence charger when there is a direct ground but will also blow if a lightning strike gets on your fence. The fuses attache directly to your fence charger or inline with the charger & fence wire. Use on the Ground fence as well if you are running a ground fence along with your Hot fence. Fuses come in packs of two for both Hot & Ground fence.