TAPERED SHAPE-GOOD SEALING: Lab seal rubber stoppers adopt a tapered shape design, which is suitable for test tubes and has good sealing performance. PREMIUM MATERIAL: Lab rubber stopper is made of natural elastic rubber material. It has moderate hardness and high elasticity, not easy to deform and environmental friendly. And it is high temperature resistant, acid and alkali resistant, not dissolve and swell in acidic liquids. EASY TO USE: Laboratory silicone stopper has excellent elasticity and flexibility. It is very easy to plug and unplug, suitable for laboratory equipment use. APPLICATIONS: Laboratory silicone bung stopper can be used in test tubes, flasks and other laboratory apparatus.Suitable for laboratory, school, home and industrial applications. WHAT YOU GET: You can get 30 PCS lab silicone stopper plugs. Its top diameter is 1.3cm/0.51inch, bottom diameter: 0.8cm/0.31inch, height: 1.7cm/0.67inch. It can be used in 12mm diameter lab tubes.