Description Size and Packing of Rubber Seal: Inner Diameter 7.5 mm/0.3 inch; Outer Diameter 12 mm/2.8 inches; Height 10 mm/0.4 inches.200 pieces of rubber stopper. Material - Made of butyl rubber it has good oil resistance and acid and resistance and can maintain stable performance in high temperatures. it is washable and reusable. It forms a good seal and is suitable for long-term storage of liquids or solids. Application - Our Butyl Rubber Stopper can be used in the laboratory and , with a good sealing effect and convenient storage. Suitable for oral liquid bottles, original solution bottles, essential oil bottles, freeze-dried bottles, etc. Suit for oral liquid bottles, original solution bottles, essential oil bottles, freeze-dried bottles, etc. Rubber Bottle Caps - These self-healing stoppers are worth it if you want to seal things, rubber drain stoppers feature an inert coating on the that helps better seal the bottle, allowing the contents to be stabilized. How to Use - These rubber caps can be punched with holes so that culture media can be injected with an needle without removing the rubber stopper. It is more clean and easier to use. Colour:Gray Material:rubber Package Contents: 200 x Rubber Stoppers Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.