The invention relates to an industrial process for the preparation of 17-hydroxy-6\u03b2,7\u03b2;15\u03b2,16\u03b2-bismethylene-3-oxo-17\u03b1-pregn-4-ene-21-carboxylic acid \u03b3-lactone of formula, and to the key-intermediates for this process. The power clamp includes a unitized body having a bore in one end thereof The power clamp also includes a piston arranged within the bore and an end cap secured to the body on the end having the bore. It is rendered easier or more difficult for an object to be judged as being a person, in accordance with whether or not the vehicle is operating in an environment with a relatively high probability that persons will be present. The plurality of cores are sandwiched between the pair of skins to form a laminate. The secondary backing may be formed of a needle-bonded synthetic fiber.