Reese Towpower 4-wire flat professional series Insta-plug kit is designed to make wiring a 4-way flat trailer connector a very simple process. Simply load the wires into the connector, close the cover, and screw it down and you are ready to use the 4-way flat connector. Features built-in circuit tester and cool blue LED (light emitting diode) indicator lights to test the trailer end circuit. Corrosion resistant and tin plated contacts for long life. Includes terminal grease.