12" x 20" or 20" x 12" Cube Core Eggcrate Return Air Grille Filter Grille + Product Details Size –

+ Product Details Size – 18"w X 34"h is the size for the duct opening measurement only

Actual Filter Size – 27 3/4"w x 23 3/4" x 1"

+ Product Details Perfect Fit & Easy Sizing - Designed for a 14" x 14" duct opening (measured at the opening)

Actual Filter Size – 31 3/4"w x 29 3/4" x 1"

12" x 20" or 20" x 12" Cube Core Eggcrate Return Air Grille Filter Grille + Product Details Size –+ Product Details Size 12" x 20" or 20" x 12" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 13. 75" X 21. 75". High Quality High quality, rust free aluminum construction with smooth finished edges and counter sunk screw holes (screws included); no sharp edges.. Installation Location sidewall and ceiling. Design Cubic core eggcrate design Offers highest airflow efficiency at almost 95%, reducing