Maintaining your instrument's humidity level is essential to preserve its playability, sound, and integrity. D'Addario's Small Instrument Humidifier easily fits in smaller cases and releases moisture evenly and slowly to maintain the proper humidity level preventing cracks, warping, and shrinkage to your instrument. Using the humidifier is as easy as moistening 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 lower. Ideal for: Care/Maintenance, Mandolin, Ukulele.