Accord ABRGWH104 Return Grille with 1/2-Inch Fin Louvered, 10-Inch x 4-Inch(Duct Opening Measurements), White Steel construction For sidewall or ceiling application 1/2-in spaced fins The number of louvered columns and mounting holes will vary based on the size of the grille ordered Listed product sizes refer to the duct opening measurements, not the register itself