The Oasis Guitar Humidifier has solved these problems by using a completely different approach. The body of Oasis is made from a specially designed fabric that allows water vapor (but not water) to pass through it. As the vapor transmission takes place, a vacuum is created and Oasis shrinks to compensate for the loss of water. By watching the Oasis shrink, you can determine when it is ready for refill. When refilling, you don’t have to guess when it is full. Simply unscrew the black cap, fill with water to the top of the container and replace the cap. Once sealed, the water tight container is your first line of defense against leaks. Humigel, the super absorbent polymer crystals inside Oasis, are your second line of defense. Humigel captures up to 500 times its weight in water in an absorbent gel matrix.