The Oasis Guitar Humidifier accomplishes the following:

You can see when Oasis is ready for refill
Long lasting humidification
Won't leak due to overfilling
Two levels of leak protection

Stabilized to Never Touch the Body of Your Instrument
You probably already know that your instrument can crack in dry weather. Repairing a cracked top of a fine guitar is both expensive and can alter the sound of your instrument. To solve this problem, guitarists have been using "sound hole" humidifiers since the 1960's. These humidifiers do have a number of drawbacks. The first is that you cannot see when they need to be refilled. When you do refill them, they can be overfilled and drip inside your expensive instrument. This is because all currently available "sound hole" humidifiers have openings to allow for water evaporation. The job of protecting the instrument against leaks is left to an absorbent medium such as a sponge or floral foam, which can be over saturated with water.