Fits 18x12 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 19.75"W X 13.75"H (18" W x 12" H Duct Opening) OD is 3/8 ID is

OD is 3/8 ID is 1/4 no color (super clear)

This added protection extends the lifespan of the connector while maintaining dependable performance in demanding environments

It has built-in damper to control air flow

If your duct opening size is 8” x 4”

Fits 18x12 Duct Opening Stamped Steel Return Air Grille Vent Cover Grille for Sidewall and Ceiling in White Surface Dimensions: 19.75"W X 13.75"H (18" W x 12" H Duct Opening) OD is 3/8 ID isThe Listed size 18"x12" is for inside duct opening measurement, actual outside dimension is 19. 75"x13. 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