SUPPLY AIR DUCT PLENUM KIT SIZE, 17.5" X 21" X 13" Long With 1/2 Flange Manufactured From 26 gauge galvanized metal.

This is a 5 piece kit that you assemble yourself to save on shipping and handling costs. It has 4 sides and an end cap for the end of the box,it has a 1/2" flange on the other side. It comes with slips, drives, and foil tape for assembling the plenum box.