The Tinman Supply Air Duct Plenum is a galvanized steel rectangle with dimensions of 21.25 x 245 x 36 inches. It is designed for both updraft and downdraft installations and is compatible with various HVAC products such as ducted evaporative coolers, packaged rooftop furnaces, ductless mini split air conditioners, outdoor wood furnaces, underfloor heating systems, dual fuel split air conditioning systems, heat pump split systems, packaged rooftop air conditioner units, central furnaces, whole house air conditioners and heaters, central air conditioners, wall heaters, central heating radiators, and air conditioner split systems. This durable and versatile plenum is an essential component for maintaining optimal airflow in various heating and cooling systems.