D'Addario Two Way Guitar HumidifierD'Addario Humidipak is the only maintenance free, two way humidity control system for guitar. It automatically maintains the optimal 45% 50% relative humidity level within your instrument case, eliminating the guesswork and potential mess related to refilling a humidifier. No more manual adjustments based on seasonal changes, geographic locations, temperature, or other factors. Note: Humidipak is designed for restoring and maintaining instrument