The D’Addario Two-Way Humidification System® (formerly the Planet Waves Humidipak®) automates the humidity control process, making it easy to maintain proper humidification for your guitar in its case. Using patented technology, the Two-Way Humidification System’s  disposable, moisture-filled packets have a leak-proof, water vapor-permeable membrane that provides two-way humidity control, allowing them to either release or absorb moisture to maintain a constant relative humidity (RH) level of 45-50 percent. The complete kit includes three packets and two pouches. The soundhole pouch houses two packets and allows both pouch compartments to descend into the soundhole to maintain the RH of the guitar body. The headstock pouch, which holds the third packet, is placed beneath the headstock in the case to help maintain the neck and fretboard. The packets are designed to be tear- and puncture-resistant. Depending on climate conditions, they should last from two to six months. Once the contents of the packets become solid, they can simply be disposed of and replaced with a fresh set of packets. Model# 80356