The two faces of the vanes are differently coloured. As the magnet passes up and down behind the vanes it cause them to rotate, displaying one colour for the region containing the liquid and another for the region containing gas. Magnetic indicators are stated in various manufacturers' literature to be most suitable for very high pressure and / or temperature and for aggressive liquids.
The two sides of the vanes have different colors, and a magnet moving up and down causes them to rotate, displaying one color for the region containing liquid and another for the region containing gas. Magnetic indicators are recommended by various manufacturers as being suitable for very high pressure and/or temperature, as well as aggressive liquids.