MRCOOL® DIY 4th Gen 18,000 BTU Multi-Zone Ceiling Mounted UnitThe MRCOOL 4th Generation DIY 18K BTU Ductless Ceiling Mounted Air Handler is an essential component of a MRCOOL DIY system. It is unique in that it can be installed between 16" ceiling joists. It also comes equipped with the elevation feature which lowers the filter down for easy maintenance. When paired with a MrCool Condenser, it is capable of achieving a 20. 75 SEER efficiency rating and has the ability to heat and cool an area of up to 375 sq ft.