Rubber Blocks, originally used as track blocks for a Army VTR (vehicle track recovery). Can be used as blocks on loading docks, boat ramps and bumper guards on heavy equipment. The thread is 3/4 in. fine thread by about 1 3/8 in. long. These work perfect for old tractors with metal wheels. Thread fits through hole and lays flat so you can drive on pavement. Measures approx 9 in. Long x 6 in. wide x 1 3/4 in. tall.