The Planet Waves Acoustic Guitar Humidifier makes it easy to properly and safely humidify your guitar. Humidifying your guitar is essential in maintaining your instrument simply moisten the sponge and hang this humidifier safely inside the sound hole of your acoustic guitar. The number one cause of major guitar repairs is lack of humidification. This 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.