The Tinman Supply Air Duct Plenum is a 26 gauge galvanized steel rectangle with 1" insulation, measuring 16 x 16 x 44 long. It is designed for both updraft and downdraft installations, making it compatible with various HVAC systems such as ducted evaporative coolers, packaged/rooftop furnaces, and mini split air conditioners. With a unit quantity of 20, this plenum is a reliable and durable accessory for maintaining optimal air flow in your home or industrial space.