10" X 4" [Duct Opening] 1-Way Air Vent Adjustable Aluminum Curved Blades Integral Multi-Shutter Damper HVAC Diffuser [Outer Dimensions: 11.75"W X 5.75"H] Return + Product Details Size - Suitable for all AC 8in diameter 12125SDCLNGBX

+ Product Details Size - 10"w X 10"h is the size for the duct opening measurement only

also referred to as T-Bar or Lay-in system

+ Product Details Size – 14" X 4" is the size for the duct opening (floor/vent hole) measurement only

actual front end outer dimensions are 31

10" X 4" [Duct Opening] 1 Way Air Vent Adjustable Aluminum Curved Blades Integral Multi Shutter Damper HVAC Diffuser [Outer Dimensions: 11.75"W X 5.75"H] Return + Product Details Size Suitable for all AC 8in diameter 12125SDCLNGBX + Product Details Size 10"w X 10"h is the size for the duct opening measurement only also referred to as T Bar or Lay in system