The Planet Waves Humidipak for Guitar is a two-way humidity control system that maintains a constant 45% relative humidity level. The patented Planet Waves Humidipak completely eliminates all the guesswork and anxiety of maintaining your instrument's proper humidity level. No more guessing if or when to refill the humidifier and worrying about drips or mess. No more manual adjustments based on seasonal changes, geographic locations, temperature, or other factors. Unlike all refillable humidifiers, the Humidipak provides true two-way purified humidity control since it adds or depletes moisture only as needed to maintain 45% RH - the ideal climate for wooden instruments. Planet Waves Humidipak for Guitar Kit includes:1 Headstock pouch 1 Soundhole pouch 3 Humidipak packettes Guitar Two-way Humidity Control System