The model 66 actuator represents over two years of product development. The unique all aluminum master cylinder incorporates the shock absorber into the master cylinder assembly. This exclusive product feature was designed into our master cylinder in order to provide the tow vehicle operator with a warning signal when the brake fluid is at a low level. This oversized master cylinder design positively provides for quicker stops when using traditional drum brakes due to the significantly higher pressures. The 6,600 lb capacity provides trailer manufacturers with greater towing capacity than traditional 6,000 lb. capacity actuators.