Iron three rings used in the laboratories are divided into three sizes: small, medium and large, which are widely used as auxiliary accessories in laboratories. Iron three rings are made of stainless steel with inner diameters of 5.3cm, 6.5cm and 8.5cm .. Outer diameters are 9.7cm, 7.8cm and 6.4cm .. Iron three rings are generally used with cross clamps as heating rings. It has stable material, acid and alkali resistance, corrosion resistance and high temperature resistance.