To provide a small vacuum pump making it possible to efficiently perform evacuation from the atmosphere to a high vacuum by using a single pump unit. The photochromic blend is made by blending a coating material or a molding material with a photochromic material. The bent section connects the inlet socket to the second outlet socket. This caudal portion is allowed to gravitationally fold distal from the skin of the canine allowing for unobstructed urination. An etching step is then carried out along the first opening and the second opening to obtain simultaneously a third depth and a fourth depth of the first opening and the second opening, respectively, with a phase shift of 180.