16" x 47 1/2" Return Air ThermO-Pan, A high-quality, sheet metal alternative for constructing return air ducts between joists and stud cavities. Consists of corrugated insulation faced with aluminum. Available in various widths, packed 25 to the box. Significantly reduces duct noises and labor. Requires no shop fabrication, Staples easily and quickly to floor joists and stud cavities, saving on labor costs and adding higher quality to the job.