UFP DX7.5L A75 Drop-N-Go Surge Actuator - Single Axle This UFP by Dexter Drop-N-Go disc brake surge actuator works by the surge or push of the trailer toward the tow vehicle. This automatically synchronizes the trailer brakes with the tow vehicle axle brakes. When the trailer pushes against the tow vehicle, the actuator telescopes together and applies the force to the master cylinder, supplying hydraulic pressure to the brakes. Product Features Capacity 7,500 lbs 1 Axle Application UFP Model 477