Aprilaire introduced the first evaporative humidifier for forced air furnace systems back in 1954. Since that time, Aprilaire continues to lead the industry in whole home humidification systems. Our evaporative humidifiers work by piping water into the distribution tray located at the top of the humidifier. The water is uniformly distributed across the width of the tray and through a scientifically designed system of outlets. It flows by gravity over the Water Panel evaporator. Dry, hot air from the HVAC system moves through the moisture-laden Water Panel evaporator. Natural evaporation takes place, meaning the water is turned to vapor, and the humidified air is circulated throughout your home.This Aprilaire 5844 Humidifier Installation Kit contains all components for step-by-step installation of an Aprilaire Whole Home Humidifier with Automatic Control, models 400, 500, 600.WHAT'S IN THE BOX (4) Screws, #8 x ", Self-Drilling 6 Duct Collar 6 Bypass Flex Duct, 3 ft. Supply Tube, "OD, 25 ft. Drain Tube, "ID, 15 ft. Hose Clamp, " Thermostat Wire, 18/2, 25 ft. Thermostat Wire, 18/2, 10 ft. Thermostat Wire, 18/5, 10 ft. (4) Twist-On Wire Nut Connectors