These Drymistat Crystal Tubes are filled with super absorbent hydra crystals that release moisture through pores in the lid. As the moisture is depleted, the crystals shrink in size. Simply refill with distilled water and the tube is good to go yet again. One tube will sufficiently humidify 25-50 cigars. Each refill usually lasts 4-6 weeks, depending on certain conditions. A tube can be filled at least 60 times, lasting you several years.