A rare earth magnetic stirring bar is a magnet that is encased in material. This material is designed to be non-reactive to fluids, so the magnets and product won’t interfere with the liquids they are immersed in. These rare earth magnetic stirring bars are used in conjunction with a device that produces a rotating magnetic field (such as this magnetic stirring hotplate), which will cause the stir bar, immersed in liquid, to spin. This spinning motion causes the reagents or liquids to mix together effectively.