Fits 24x10 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 25.75"W X 11.75"H (24" W x 10" H Duct Opening) The listed size 12" x

The listed size 12" x 4" is for the inside duct opening measurement

Simple roundflow design for smooth air flow

actual outside dimension is 18

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

Fits 24x10 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 25.75"W X 11.75"H (24" W x 10" H Duct Opening) The listed size 12" xThe Listed size 24"x10" is for inside duct opening measurement, actual outside dimension is 25. 75"x11. 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