XIKAR Crystal 250 Humidifier is filled with a special hi-tech gel capable of absorbing 450 times its weight in fluid! When dry, the gel looks like sea salt. When fully charged, the gel looks like large chunks of gelatin. Works best when used with XIKAR Propylene Glycol solution, as other solutions may damage your humidifier. When used with XIKAR Propylene Glycol solution, crystal gel generates a constant humidity of 70%. XIKAR Crystal 250 Humidifier if for use with humidors that hold up to 250 cigars. A steel and magnet attachment system keeps the humidifier firmly attached to your humidor lid. The Crystal Gel shrinks as it loses moisture telling you exactly when it's time to refill! Measures 6 1/2" diameter x 7/8" thick.*Please note that this product has changed and it now comes in dry form. To use, you must activate the crystals with PG solution (recommended) or distilled water.