<ul></ul><b> Adjustable Air Register – Diffuser for sidewall or ceiling applications. The listed size 10“w X 8”h is for duct opening measurement only, Actual outsize overall dimensions is 12“ wide by 10” high. </b> <ul></ul><b>Difference Between grilles, registers, diffusers and vents：</b> <ul><li>Grille – a series of deflectors in the shape of blades or fins fixed in a frame to allow air to pass through from duct to room space</li> <li>Register – a grille attached with a damper or valve to control the air flow volume</li> <li>Diffuser – a unit with duct connecting piece and a larger face piece with multiple blades to spread out air flow to multiple directions. Examples are drop ceiling T-bar diffusers, round ceiling diffusers and adjustable blade sidewall diffusers.</li></ul> <b>Size Selection Guide</b><ol><li>Measure the size of the air duct opening(the size of the “hole” ). </li><li>Select the listed size that match the duct opening size.</li> <li>The outside or overall size is 2” larger for both width and length so it can cover the “hole”.</li> <li>Do not use outside measurement for size selection.</li></ol