The REESE Towpower 4-Flat, trailer end connector with built-in LED tester allows for an electrical connection between the towing trailer and the towing vehicle. Simply wire 4 connections to activate the trailer's stop, turn and tail lights. This unit also features a built-in LED circuit tester to constantly monitor the electrical circuit and indicate when electricity is present. Reese is the market leader in automotive and recreational product solutions, engineered and designed to meet the demands for work and active lifestyles. Reese Towpower pioneered the technology that has set the standard for today's most advanced towing systems. We cater to the towing needs of everyone from recreation enthusiasts to heavy-duty agriculture users by manufacturing the largest selection of receiver hitches; ball mounts and hitch balls; trailer and hitch locks; couplers, jacks and winches; and electrical and lighting components that meet and exceed industry standards.