The number one cause of major guitar repairs is lack of humidification. Humidifying your guitar is an essential step in maintaining your instrument. The best selling D'Addario Acoustic Guitar Humidifier makes it easy to properly and safely humidify your guitar. The Humidifier hangs safely in the sound hole suspend by the instruments strings so it never touches the body of the instrument. Simply moisten the sponge, install and that's it. The humidifier releases the moisture slowly and evenly keeping your guitar perfectly humidified. When the sponge becomes completely dry, moisten it again and insert back into the soundhole.