Rubber stoppers are very necessary and effective for containing the liquids in your test tubes and even flasks. The good thing with these stoppers is that they are made to specifically fit very effectively and tightly. Made from several kinds of rubbers, they help in preventing the chemicals in the test tubes or flasks from spilling or leaking. Depending on the size of your flasks and test tubes you can find the exact rubber stopper that will match perfectly. They can be used for whatever you want them to be used for, whether for scientific, commercial or even industrial uses.