6" x 8" or 8" x 6" Cube Core Eggcrate Return Air Grille Fixed Blades while the included installation screws

while the included installation screws make setup quick and hassle-free

+ Product Details Size – 12" x 18" or 18" x 12" is the size for the duct opening measurement only

+ Product Details Size - 20"w X 36"h is the size for the duct opening measurement only

+ Product Details Size - 28"w X 36"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 34 5/8" width X 8 5/8" height

6" x 8" or 8" x 6" Cube Core Eggcrate Return Air Grille Fixed Blades while the included installation screws+ Product Details Size 6" x 8" or 8" x 6" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 7. 75" width X 9. 75" height. 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%,