Hydrometers and similar floating instruments, thermometers, pyrometers, barometers, hygrometers and psychrometers, instruments and apparatus for measuring or checking the flow, level, pressure or other variables of liquids or gases except navigational, hydrological or meteorological instruments and appliances, gas or liquid supply meters, and automatic regulating or controlling instruments and apparatus for physical or chemical analysis, for measuring or checking viscosity, porosity, expansion, surface tension or the like, or for measuring or checking quantities of heat, sound or light

CPC v2.1 class (Hydrometers and similar floating instruments, thermometers, pyrometers, barometers, hygrometers and psychrometers, instruments and apparatus for measuring or checking the flow, level, pressure or other variables of liquids or gases except navigational, hydrological or meteorological instruments and appliances, gas or liquid supply meters, and automatic regulating or controlling instruments and apparatus for physical or chemical analysis, for measuring or checking viscosity, porosity, expansion, surface tension or the like, or for measuring or checking quantities of heat, sound or light) within 'Instruments and appliances for measuring, checking, testing, navigating and other purposes, except optical instruments; industrial process control equipment; parts and accessories thereof'. UN Central Product Classification grouping of related products at this level.