Maintaining the humidity level of your instrument is essential to preserve its playability, sound and integrity. The D'Addario humidifier for small instruments fits easily into small cases and releases moisture evenly and slowly to maintain the correct humidity level, preventing cracking, warping and shrinking of your instrument. Using the humidifier is as simple as dampening the sponge when it becomes dry. The humidifier can also be used in conjunction with the D'Addario Soundhole humidifier (GH) for acoustic guitar cases when your humidity is consistently 20% or less.