This stopper is made from food grade silicone so it is safe for use in food and drinks. This stopper is made to fit the 1000mL Pyrex Flasks (#9).
Do not be fooled by cheap stoppers. Rubber stoppers can contaminate any item it touches. Rubber stoppers can also change the flavor of food or drinks that they come in contact with. Only use food grade silicone for use in food or drink.