When your MES or HD Series air conditioner can't be in the same area its cooling this plenum can be bolted to the front of the evaporator so you can duct air back into the evaporator via 2- 4" flexible ducting(Not included). Constructed of stainless steel. Cover will be cut where it says Cruise N Comfort and the perforated holes and plenum will be installed if purchased at the time of the unit purchase.