Porta-Pak is the top-selling portion-control deodorizer in the world. Walex manufactures it the odor control experts. The slide-zipper bag contains 10 water-soluble drop-in treatments. The Fresh-scented water-soluble packet controls odors breaks down waste and paper and lubricates valves and seals. Porta-Pak s premium formula works even in the extreme heat of summer. The high-performance packet is formaldehyde-free. To use Porta-Pak drop one packet in the toilet and flush adding water. One Porta-Pak provides week-long odor control from 2.5 gallons up to a 40-gallon black tank.