20" X 30" or 30" X 20" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 21.75 X 31.75] w28h28 + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 22" or 22" x 12" duct opening (measured at the opening)

these heavy-duty louvers are ideal for use in attics

Example: If your opening is 14" tall by 20" wide

Actual Filter Size – 33 3/4"w x 11 3/4" x 1"

+ Product Details Size & Compatibilty - The 16" to 12" round metal pipe reducer & increaser 30 gauge is compatible with duct 16" to 12"

20" X 30" or 30" X 20" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 21.75 X 31.75] w28h28 + Product Details Perfect Fit+ Product Details Size 12"w X 30"h or 30" x 12" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 13. 75" width X 31. 75" height. High Quality High grade steel construction meant for high foot traffic areas. Installation Location Floor. Design Easy drop in installation Powder Coat Finish Smooth, shiny, scratch resistant, with no sharp edges. Looks like it was just waxed. Quality Packaging Carefully