Most guitar humidifiers are only concerned with getting moisture into your acoustic, but the Planet Waves Two-Way Humidification System brings a two-fold approach with a dual packet system that regulates both the addition and removal of moisture. Designed to keep your instrument at an ideal 45-50% relative humidity regardless of season, temperature, geography, or indoor atmosphere, the Two-Way is the perfect set-it-and-forget-it humidifier that will keep your guitar sounding as fresh as the day you bought it.