The cleaning difficulty of the alien sex doll equipped with movable tentacles is comparable to that of precision instrument maintenance. The 32 hydraulic joints in each tentacle need to be washed section by section with a micro pulse water gun to prevent lubricant residue from causing silicone aging. In contrast, the iconic cat ears or tails of the hentai sex doll, although exaggerated in shape, can be cleaned 360 degrees without dead ends through ultrasonic vibrators. This difference in structural complexity makes the maintenance time of alien dolls 3.7 times that of hentai products on average.