50,000 Pound Lifting Capacity is a factory add-on to the line of Trailer Stabilizing Jacks to increase the capacity range from 40,000 pounds. This option can not be added to the Economy Line.Trailer Jacks are heavy duty dome shaped, and have a 14 inch diameter base for maximum leveling stability. These jacks are used to prevent up-ending semi-trailers when they are not connected to a tractor during loading and unloading operations. Also used to level trailers parked on sloped ground and to prevent landing gear from sinking into a soft surface. High strength steel construction. Steel collar welded to steel tube and inserted into a 1.5 inch diameter cold rolled steel screw with acme thread. Flush-type zerk fitting for lubricating ACME screw. 3" heavy duty steel tube welded to top of base. Powder coat safety yellow finish. Includes reflective collar for visibility at night. Meets OSHA regulations when used with wheel chocks.