This product is designed for heavy duty truck and trailer shop use, rail and bus work and portable for roadside service calls. The narrow chassis design fits easily between tandem wheels, while the chassis base is contoured so wheels make contact with the ground when the jack is not under the load. It raises the wheels off the ground when under load to prevent damage. The overload and bypass safety valves prevent the jack from being used beyond its rated capacity and ram over-extensions. It has a self-retracting ram, as well as an integrated filter to protect the air motor.