Return air boxTake advantage of the durable 26 gauge galvanized steel construction of this Master Flow Return Air Box to equip your HVAC system with a long lasting air return box. wall grill (not included) for return air needs. Provides collecting port for central return duct Traditionally used in a ceiling or wall application as an air return chamber, acting as a convenient connection for air return Compatible with pipe or flexible duct 26g coated, galvanized