FBS – Fiberglass Backed Supply Air Diffusers from The Duct Shop are 24” x 24” and perfect for use in T-Bar ceilings for supply of Heat and Air Conditioning. FBS has a bright gloss white perforated face and a fiberglass back which is per-scored for 4” through 14” diameter collars. You will also need to purchase a Dovetail Start Collar to connect your duct to the register
