Replacement Plug for USCAR Socket (56229) by CURT®. 7-Way Vehicle End with 24″ Bonded Wire. Material: Plastic. A CURT custom wiring connector (sometimes called a T-connector) is a simple, plug-and-play electrical device that eliminates the need for cutting, splicing and soldering when installing vehicle-to-trailer wiring. Most vehicles do not come ready to tow. Unless your vehicle has a towing package, it is probably not equipped with a trailer wiring connector. This is where CURT’s custom wiring connectors come into play.