Planet Waves has collaborated with Humidipak to develop the first dual humidity control system that provides a consistent 45% - 50% humidity level. The patented Planet Waves Humidipak eliminates all guesswork and speculation about maintaining the proper moisture content of your instrument. Now there's no more guessing where and when to refill the humidifier.
You also no longer have to worry about spilling or getting anything dirty. You no longer have to make manual adjustments based on seasonal changes, geographic location, temperature or other factors. Unlike other refillable humidifiers, the Humidipak provides true dual humidity control.
To maintain the ideal climate for wooden instruments, the Humidipak independently increases or decreases the humidifying liquid.
Features:
Automatic control system constant moisture content of 45% - 50% including pocket for the sound hole and for the headstock 3 pieces humidipaks.
Humidity is regulated in a simple and effective way . Howevver the main pouch that should fit in the sound hole is way too large. In my Martin D-28 (not the smallest) it sticks out and touches the bottom and side of the hole. Further as it is a soft bag it doesn't stay put when you carry the case around or position it different as flat on it's back. Had to put both pouches at the head stock end; imo that should work just as well as humidity will diffuse throughout the case and the guitar anyway. It's not the cheapest option but it offers benefis others doen't have.