What the Bio-active stones do: Maifan Stones are a special mineral rock used in Chinese medicine to treat various skin diseases. It contains micro-nutrient elements, such as calcium, iron, zinc, magnesium, copper and selenium. It is made of 4 component parts, 2 ion boxes, a filter sponge, Calcium Sulfite Stones and Maifan Stones. This filter reduces 80-90% of chlorine present in the water. These Mineral Stones soften and rejuvenate skin, restores balance to oil glands and can help reduce the risk of Asthma.