Heavy duty projects require heavy duty wiring, and 4 gauge cable is best used to convey primary power to items that require a lot of it. You can use 4 gauge wire in a car battery, a small house’s circuit breaker panel, a large sound system’s main amp, and more applications. These cables can carry an immense amount of juice reliably and safely for years at a time, making projects of significant scale not just possible but easy in many cases. While the detail wiring required to make projects and vehicles work is small in gauge and generally comes in plain spools for the end user to manipulate, 4 gauge wire kits often have more accessories so they can be quickly hooked up to power. While 4 gauge wire might be less versatile than smaller wires, it’s much more hardy.