Aprilaire Model 600M HumidifierAprilaire Model 600M For Home Sizes up to 4,000 Sq. Ft. Requires a Plenum opening of 10" Width and 12 3 4" Height Included: Template and Instruction manual, Aprilaire 600M Humidifier with a built in bypass damper, Aprilaire Part #35 Water Panel, a Manual Humidistat, 1 Self Piercing Saddle Valve, and 1 24V Transformer Product must be installed by a qualified heating and air conditioning contractor. Failure to do so could result in serious injury from