A cap comprising a generally conical wall positioned beneath an opening in the cap and having a plurality of striations formed therein to facilitate penetration of the cap by a fluid transfer device. The speed reducer may be incorporated in the plurality of industrial machines, respectively, so that the position of a meshing portion when the external gear is assembled to the internal gear has a specific phase relationship common to the plurality of industrial machines with respect to a specific part of an industrial machine in which the speed reducer is incorporated. The fabrication method includes porous silicon formation and silicon polishing in HF solution. A multiple input signature register or other such equivalent data compressing means provide the necessary data compression for reducing the volume of the test results that can be observed during scan by the tester to detect the presence of any fault that was observed. In accordance with this method, an aspherical optical element having a higher precision than ever can be formed at reduced cost by a replica method involving the addition of a resin layer to the surface of a spherical or flat substrate.