Description: These stir bars are magnetic, and coated in PTFE, no harm to human body, and heat resistant to 250 celsius degree The PTFE coatings are intended to be chemically inert, not contaminating or reacting with the reaction mixture they are in Octagon magnetic stirring bars with integral ring are the most commonly used shape. Their interrupted profile provides greater surface area and added turbulence when compared to the smooth surface of cylindrical bars. ring aids in reducing friction and chattering Magnetic stirrers can only be used for relatively small experiments of 4 liters or less.The mixing process is quieter and more efficient, and the stirrer is not exposed to the external transmission component so it is not easily damaged Stir bars help to build a relatively economical, environmentally friendly, and safe device that can greatly save manpower and reduce the use rate of flames, and relatively improve the safety of laboratories and home brewing Package Includes:(8 Pack) 1 Piece stir bar