[Intelligent ]safest and most responsive system you can install. trailer brake controllers automatically sense when your tow vehicle slows down or stops. This type of brake controller replicate your own intensity for your trailer's brakes - whether you slow to a gradual stop or have to on your brakes. [Easy to display]LED Digital display screens show the voltage delivery going from the brake controller to the trailer's brakes. Easy to read, easy to observe vehicle conditions in real time.In case of emergencies, make adjustments in time. [ and more stable]Fits 1 to 4 axle (2 to 8 brakes) trailers to deliver a signal from your vehicle's brakes to your trailer,both quantity of power (result) and rate of the program (sync) can be adjusted to fit your inclination, the street conditions, and kind of trailer,increase the safety of driving.Requires no leveling. [Quick installation and use]Wiring ports are available for vehicle-specific brake controller harnesses and provide a quick connection between the controller and the towing vehicle for quick and easy installation or removal. [Muti-function]Brake Control for Trailer Tow,for example: RV, trailer, truck, sightseeing car. Colour:Black Material:plastic+metal Package Contents: 4 Set x Brake Controller Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.