SUPPLY AIR DUCT PLENUM 21 X 21 X 36 LONG GALVANIZED STEEL 26 GAUGE. IF YOU DON’T SEE THE SIZE YOU NEED LET ME KNOW AND I WILL BUILD THE SIZE YOU NEED JUST FOR YOU. (tools shown in some photos are not included). MADE IN THE USA! THANKS FOR LOOKING AND PLEASE VISIT MY STORE FOR MORE GREAT DEALS!