M4O standard multi-zone ductless outdoor unit work with up to four (M40) indoor systems. Each indoor system comes with its own control, so you can set each room to a different temperature. Free match with any wall mount, ceiling cassette, ducted system, or console. DC Inverter Heat Pump provides year-round comfort allowing the unit to reverse the refrigerant process in cold weather, by extracting outside heat and transferring inside. Excellent for house additions without forced air heating systems or where ductwork is not possible.