OTC 1794A 1000 lbs Capacity Air-Assisted High-Lift Transmission Jack Air-assist primary stage for rapidly raising the mounting head activated by depressing foot pedal Hydraulic secondary stage for precise operator control activated by a hand pump to raise the load and a release knob to lower the load Big easy-to-grip knobs that make mounting head adjustments simple and a safety chain for securing the load Wide leg base with 4 inch polyurethane swivel wheels that provide stability and easy maneuvering 20-Ton capacity jack with a maximum extension of 17-1/2 inch