12" BUTTERFLY DAMPER - For T-Bar, Drop Ceiling Grilles, (12" round duct opening) Sheet Metal/Adjustable Elbow Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 18" X 6" duct openings

actual front end outer dimensions are approximately 26 5/8" width X 28 5/8" height

Our coils have a a very high PSI burst pressure

you can watch this informative video tutorial: How to Measure Your Vent Hole Before Ordering a Grille

actual front end outer dimensions are approximately 36 5/8" width X 8 5/8" height

12" BUTTERFLY DAMPER - For T-Bar, Drop Ceiling Grilles, (12" round duct opening) Sheet Metal/Adjustable Elbow Ideal for Walls & Ceilings:+ Product Details Size 12" round duct opening Heavy Gauge Steel Heavier gauge than needed, built for durability and long life in mind, but still very thin. Installation Location Ceiling. Design This airflow control component are made to connect to a drop ceiling lay in diffuser grille. Powder Coat Finish smooth, shiny, scratch resistant, beautiful. Looks like it was just waxed. + Product Description Introducing the 6" Butterfly Damper Your Solution