What a great name for a water saving device! This Toilet Tank Bag will help save water with every flush. To use, just fill it up with water and place it in the tank. Once that is done, you never have to think about it again. It is made out of noncorrosive materials that resist microbes and fungal growth. The anti-evaporation airlock snap means the bag never needs refilling. An easy and inexpensive water saving trick.