D&rsquo;Addario Accessories Humidipak Two-Way Humidification System &ndash; Automatically Adjusts to Maintain Constant 45% Relative Humidity Level Within Guitar Case &ndash; Protects Instrument from Humidity Damage TWO-WAY HUMIDITY CONTROL  DAddario Accessories Humidipak Two-Way Humidification System is the only maintenance-free two-way humidity control system for guitars. It automatically maintains the optimal 45-50% relative humidity level within your instrument case by adding or depleting moisture as necessary. PROTECT YOUR INSTRUMENT  The patented two-way purified humidity control system protects your instrument against warping, cracks and other damage caused by lack of humidification. This system eliminates the guesswork and anxiety of maintaining your instruments proper humidity level. MAINTENANCE-FREE  Unlike refillable humidifiers, the DAddario system is maintenance-free. It is long lasting and does not require any adjustments based on seasonal temperature changes or geographic locations. No water, no drips, no mess. INCLUDES  The Humidipak two-way humidification kit includes three Humidipaks, a soft mesh headstock pouch and a soft mesh soundhole pouch that wont harm your instrument's finish. MADE IN THE USA - D'Addario Accessories is known for innovative, problem-solving, quality musical accessories that are proudly designed, engineered, and manufactured in the USA to the most stringent quality controls in the industry.