Fits 20x8 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 21.75"W X 9.75"H (20" W x 8" H Duct Opening) The Listed size 20"x6" is

The Listed size 20"x6" is for inside duct opening measurement

This product has listed size 8“w X 4”h is for duct opening measurement only

actual outside dimension is 14" X 14"

The Listed size 10"x 4" is for inside duct opening measurement

The outside or overall size is 2

Fits 20x8 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 21.75"W X 9.75"H (20" W x 8" H Duct Opening) The Listed size 20"x6" isThe Listed size 20"x8" is for inside duct opening measurement, actual outside dimension is 21. 75"x9. 75" Stamped Face Steel Construction with 1 2" fin spacing for high air flow applications. Screws are included for easy installation White Powder coating with matte finish Individually packed with cardboard box for ultra protection