The OH-4 Humigel™ Replacement Kit is of critical importance for the successful use of our humidifiers. The ONLY reason for the use of the crystals is to reduce the risk of damage to your instrument from potential leaks. Humigel™ crystals are very hygroscopic and hold up to 400 times their weight in water. We add .6 cc’s of crystals prior to packaging. This is such a small quantity that you can barely see them at the bottom of the humidifier. The best way to tell if they are present is to shake the humidifier and hear them rattle around. .6 cc’s is the amount needed to turn the water into jelly. Unlike water, the jelly is semi-solid and will contain the water should the humidifier become damaged. With the crystals present, a damaged humidifier will become damp or have water spots but will not leak into your instrument.