Check the listing for details. D'Addario Humidipak Automatic Humidity Control System Replacement 3-Pack. Condition: New. Listed at 18.99 USD. D'Addario Humidipak Automatic Humidity Control System Replacement 3-Pack The Two-Way Humidification System (formerly 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. Unlike refillable humidifiers, this system provides true "two-way" purified humidity control by adding and removing moisture on demand. No more manual adjustments based on seasonal changes, geographic locations, temperature, or other factors. The included three humidification packets last between 2 and 6 months and should always be kept in a sealed environment like a hard-shell case. Features: -The first two-way humidity control that maintains a constant 45%-50% relative humidity level within your instruments case -Protects your instrument against warping, cracks and other damage cause by lack of humidification -No more manual adjustments based on seasonal changes, geographic locations, temperature, or other factors Unlike refillable humidifiers -Eliminates the guesswork and anxiety of maintaining your instrument's proper humidity level -No water, no drips, no mess -Custom made by Boveda for D'Addario