Oasis Bright White WaterGuard Kit, model 033963-021, is a NSF approved accessory. It eliminates glugs, leaks, and spills. This useful unit stops glugging that can put stress in the bottle causing cracks and pinhole leaks. It prevents leaks and spills during bottle change-out with innovative design. The check valve within the air filter reduces flooding due to pinholes or cracks in bottles. Cleaning is a snap with the removable flow divider. WaterGuard VI has no screws or welds to make contact with the water. It increases sealing effectiveness with new reservoir seal and keeps dust, bugs and pollen out of cooler reservoir.