The Xikar Crystal 250 cigar humidifier contains a special polymer gel capable of absorbing up to 450 times its weight in fluid. In any climate, the Crystal 250 Humidifier will release and absorb just enough moisture to maintain a perfect 70% humidity in your humidor. This unique automatic humidity control is achieved by using our recommended Propylene Glycol solution – see http://www.thecigarsmoker.com/solution-cigar-humidifiers-p-1066.html