Instruct: Classify a review as either positive or negative.
Query: These do not make a tight seal. Don't buy unless you have a pump!

I thought these would work like a cork only better. They don't. From what I've read, you should not use these unless you also have "the pump". The directions on the package and on the web site indicate you can use these by themselves. However, the directions are not very precise or clear. I cannot get them to stay in the bottle, to "pump" or make any type of seal. They just sit on top of the bottle. In fact, when I try to push them down into the bottle, they slide right back up! What a waste of money.