MV360S ROUND DIFFUSER GRILLE. Ceiling diffuser grille with adjustable collar. NOTE: Product includes adjustable airflow damper - but no backdraft damper. See related products for backdraft dampers. The Model MV with its unique design and contractor friendly engineering saves money by reducing installation time by up to 80%. A Diffuser, Boot and Damper all in one, it installs in seconds with just a few easy steps. FEATURES: - Will accept 4, 5, and 6 inch duct sizes using tear-away bands so there is no cutting required. - Mounting clips rotate into position securing the unit to the ceiling material quickly and easily. - An adjustable fixed-position damper allows you to regulate the mount of air moving through the grille. - Includes 1 tie strap A= 9 3/8 B= 7 1/8 C= 5/8 D= 1 3/8 E= 3 1/4 F= 5 1/4 G= 7 1/4 Ducting does not fit flush against the diffuser. Diffuser fits a 7-1/8" hole.