Stir bars, also known as magnetic stirrers, are small magnetic bars used to mix liquids in beakers, flasks, or other containers. They are placed inside the container and rotated by a magnetic stirring plate, creating a vortex that mixes the liquid., Stir bars are typically coated with Teflon or other inert materials to prevent contamination of the liquid. They are available in various sizes and shapes to suit different container sizes and mixing requirements.