This supply air duct plenum is made of galvanized steel with a 26 gauge thickness. Measuring 20 x 25 x 30 inches, it is designed for use with various HVAC and refrigeration systems, including ducted evaporative cooler, packaged/rooftop furnace, ductless mini split air conditioner, outdoor wood furnace, underfloor heating system, dual fuel split air conditioning system, heat pump split system, packaged/rooftop air conditioner unit, central furnace, whole house air conditioner & heater, central air conditioner, wall heater, and central heating radiator. Its rectangular shape and compatible features, such as updraft and downdraft installation, make it a versatile choice for any HVAC and refrigeration setup. With a unit quantity of 20, this supply air duct plenum is sure to meet your needs.