The RH STAYFRESH Humidifier 77% is perfect for keeping your cigars fresh. It is a 2-Way Humidity Control Pak designed to accurately maintain the humidity environment in your humidor. It is made of all-natural plant-based materials. The RH STAYFRESH pak has a specially designed membrane that allows the transfer of water vapors without harming your cigars. The RH STAYFRESH pak releases purified water vapor, it captures excess humidity, does not require maintenance, and it does not release any harmful gases or toxic elements. RH STAYFRESH Humidifier paks do not require liquids or salts in order to work. Thereby, greatly reducing the chances of your cigars being damaged due to leakage or cross-contamination. To use, simply put the required number of RH STAYFRESH pak(s) in your humidor along with the provided indicator card. When the pak feels firm and dry or if the card changes from pink to blue, it's time to replace it. Each pak is made to last approximately 90 days (120-day are paks also available). Use one pak for every 50 cigars your humidor can hold, plus one additional pak (for example, 2 packets for a 50-cigar humidor, 3 pak for a 100-cigar humidor).