Magnetic stirring bars provide effective stirring of samples via magnetic manipulation. Many models feature an octagonal shape with a central integrated pivot ring for optimal turbulence while stirring thanks to a greater surface area. Commonly coated in Teflon to provide chemical inertness; occasionally glass will be the coating for use with most liquid alkali metals and alkali metal solutions in ammonia. Both of these coatings are inert and will not contaminate or react with the reaction solution.