Oasis OH-6 Case Humidifier You can see when Oasis is ready for refill Long lasting humidification Won't leak due to overfilling Two levels of leak protection The huge success of the original Blue Oasis sound-hole humidifier has brought many inquiries about ways to provide humidification for other instruments including violins, violas, cellos, mandolins, ukuleles, jazz guitars and guitars with flat top cases