Speedi-Products EX-DFRP 04 4-Inch Diameter Round Adjustable Plastic Diffuser, White Speedi-Exhaust Products are made in the USA Ideal for exhaust and supply air duct systems and fans This plastic round adjustable ceiling diffuser is easy to install using a stainless steel grip clip which provides a snug fit Seal joints with approved duct mastic sealants & tapes Consult your local building codes for approved installation practices