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. Humidipak comes with 3 packets and a soft mesh pouch that will not harm your instrument's finish. These packets last between 2 and 6 months and should always be kept in a sealed environment like a hard-shell case. Once the packets become firm, discard and replace using the 3 refills that come in the Humidipak Replacement Pack (PW-HPRP-03). This all new, reformulated, patented two-way humidification system maintains 45-50% relative humidity which eliminates all maintenance and guesswork. Note: Humidipak is designed for restoring and maintaining instrument humidity. This product is not intended for de-humidification in high humidity environments. 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. D'Addario is known for innovative, problem-solving, quality musical accessories, offering a complete line of award-winning accessories including cables, picks, tuners, capos, straps, humidifiers, maintenance tools and more.