Waterproof Anti High temperature White Solide Rubber Hole Sealing Plug Bung Tapered Silicone Rubber Cone Plug Stopper for Test tube This is made of high quality rubber material. Not easy to deformation and crack, smooth surface, compact texture, slightly elastic, strong and reliable seal, complete number. Chemical instruments without abrasives can generally be sealed with rubber plugs. Rubber plugs come in different sizes. The gigger the number , the bigger the volume.The rubber plug can be drilled with a plungerand inserted into a glass tube to form a connecting device that can export gas from the sealed container.