All vehicle specific brake control wiring harnesses are available in 1-Plug or 2-Plug styles.1-Plug units are designed for brake controls manufactured with electrical wiring mounted on the back of the unit, otherwise known as a pigtail.Wiring harnesses must be spliced into the existing pigtail to allow the vehicle specific plug to be installed.2-Plug units are designed for brake controls that have a wiring port built into the back of the unit.Simply plug the brake control end of the wiring harness into the back of the brake control and the vehicle end into the automobile's port.Brake controls that utilise the 2-plug style of wiring harness will be identified with the Plug and Play logo.