Venting Exhaust System Dryer Box; Item Dryer Box; Size 12-1/2 Inch Width x 4-3/8 Inch Depth x 21 Inch Height; Material Thickness 22 Gauge; Material Aluminized Steel; Used On Item Upward Venting Exhaust System; Applicable Standard UL (Canada and US); Inside Size 9-1/2 Inch Width x 18-1/4 Inch Height; Distance from the Nailing Flange to the Rear of Box 3-1/2 Inch