8"W X 18"H [Duct Opening] Steel Air Vent Return Grille - HVAC VENT DUCT COVER DIFFUSER - [Outer Dimensions: 9.75"W X 19.75"H] Filter Grille + Product Details Size - Drop Ceilings / Aluminum The set includes a FG1836 HP-1

+ Product Details Size - 20"w X 8"h is the size for the duct opening measurement only

+ Product Details Size - 34"w X 28"h X 2"d (for duct opening measurement only)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 30" OR 30" x 28" duct opening (measured at the opening)

Actual Filter Size – 17 3/4"w x 21 3/4" x 1"

Its linear bar design maximizes ventilation

8"W X 18"H [Duct Opening] Steel Air Vent Return Grille HVAC VENT DUCT COVER DIFFUSER [Outer Dimensions: 9.75"W X 19.75"H] Filter Grille + Product Details Size Drop Ceilings Aluminum The set includes a FG1836 HP 1 + Product Details Size 20"w X 8"h is the size for the duct opening measurement only + Product Details Size 34"w X 28"h X 2"d (for duct opening measurement only)