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) Actual outside measurement is 16"

Actual outside measurement is 16" x 10"

Stamped Face Steel Construction with 1/2" fin spacing for high air flow applications

1/2" ID for high water flow

actual outsize overall dimensions is 13

The Listed size 24"x20" is for inside duct opening measurement

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) Actual outside measurement is 16"The 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