UFP DX7.5L A60 Disc Brake Surge Actuator - Tandem Axle This UFP by Dexter 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 UPF Model 34044 Capacity 7,500 lbs Tandem Axle Application F