16"w x 16"h 4-way aluminum curved blade adjustable air supply hvac diffuser - full control vertical/horizontal airflow direction - vent duct cover outer dimensions: 17.65"w x 17.65"h

16"w x 16"h is the size for the duct opening measurement only, actual front end outer dimensions are 17.65" width x 17.65" height - see below in description how to measure a grille,never rust - high quality rigid aluminum,4-way adjustale louvers - full control vertical/horizontal airflow direction,rigid design - noise free components - no vibrating louvers etc.,replacement-furnace-filters never rust - high quality rigid aluminum|4-way adjustale louvers - full control vertical/horizontal airflow direction|rigid design - noise free components - no vibrating louvers etc.|replacement-furnace-filters