Review (4/5): Don't get tongue bite! Keep pipe tobacco fresh or rejuvenate a dried out tin. Doesn't prevent cancer.
These preserve the freshness of pipe tobacco after you open the tin and before it gets all dried out. But, if you smoke like a chimney, you probably finish a tin of tobacco way before it goes stale. I tend to smoke my pipe more in the winter months, so I have unfinished tins of tobacco laying around getting dried out. Just soak one of these buttons in water for a moment and then place it in the tin with the tobacco. In a day or two, your dried out tobacco is good as new! And just as bad for you as new!
These sell for anywhere between $1 and $5 each in pipe & cigar stores.