3-pack of replacement packets for the Planet Waves Humidipak Humidity Control System, the first maintenance free, two-way humidity control system that preserves a constant 45%-50% relative humidity level within your instrument's case. 3 replacement packs for the Planet Waves Humidipak system Automatic humidity control 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 Lean more and view FAQ's at PlanetWaves.com