This listing is for two packs. Do not remove unite housing. Directions for use It is a violation of Federal law to use this product in a manner inconsistent with its labeling.1. Do not use in: Humidifiers, humidifier sections of air conditioning systems on evaporative coolers.2. Clean unit in pan, pad side down.3. Place unit in pan, pad side down.4. In pans with drain connections, place unit under the cooling coil in the middle of pan length.5. Unit must be in contact with condensate.6. This unit is designed and approved only for use in drain pans of air conditioning systems and refrigeration systems.7. Has been proven to control the growth of, or inactivate, Legionnaires' Disease Bacteria in experimental laboratory conditions for 2 months when approximately 15 gallons of water flow over CDC Anti-Clog #1 units per day. We recommend replacing CDC Anti-Clog #1 units, every 2 months, if that is the intent. For industrial use only.R1R4S4