The DAddario Ukulele Humidifier Pro is DAddarios first ukulele humidifier. This humidifier has been designed to fit in the soundhole of your ukulele. The easy-to-remove rubber cap makes re-soaking the hydrophilic sponge a quick and easy process. This humidifiers sponge has been designed to hold up to 12x its own weight in water for better hydration over a longer period of time. Using the UHP humidifier pro will help maintain and protect your precious instrument.