20" X 20" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 21.75 X 21.75] Fixed Blades with Damper Actual Filter Size – 17 Compatible With Duct 7in Applications This sheet metal DDAG-A-1212

Actual Filter Size – 17 3/4"w x 7 3/4" x 1"

And is classified as Class 1 Fire Proof - B1

Insulation – A thick blanket of fiberglass insulation provides you with an R-Value of 8

+ Product Details Size - 18"w X 30"h X 2"d (for duct opening measurement only)

+ Product Details Size - 24"w X 4"h is the size for the duct opening measurement only

20" X 20" Heavy Duty Floor Grille Fixed Blades Air Grille Brown [Outer Dimensions: 21.75 X 21.75] Fixed Blades with Damper Actual Filter Size – 17 Compatible With Duct 7in Applications This sheet metal DDAG A 1212 Actual Filter Size – 17 3 4"w x 7 3 4" x 1" And is classified as Class 1 Fire Proof B1