This Master Flow 24 in. x 24 in. x 24 in. Duct Board Plenum Kit - R6.0 lets you easily create an air mixing chamber for your furnace before your ventilation system accepts it. The duct board reduces ventilation system noise and reduces condensation for improved performance. Its high 6.0 R-value provides thermal efficiency. Kit includes 4 sides and top. Open bottom to attach to air system. Product is "knocked down" for shipping and must be assembled.