Features More holding power and works easier than ever Works on all surfaces and most trailer axles (round or square) from 10" - 15" wheels To use, just place the boat trailer jack under the axle and drive forward or reverse a few inches Quick change automatically raises the trailer to the proper height for changing tires, lubricating or replacing wheel bearings and more Specifications Dimension: 11.13" H x 3.75" W x 17.25" L Weight: 3.57 lbs