Ceiling Diffuser with damper, 4 way, white plastic. Diffuser measures approx. 11.5" x 11.5" (290 x 290 mm). Cut 9.25" (235 mm) dia. hole in ceiling to fit. Round spigot will accommodate 6", 7" and 8" ( 150 ,175, 200 mm) dia. round flexible ducting; remove unwanted sections before installing. The diffuser clamps to the ceiling, so its position relative to the adjacent walls can be adjusted if not perfectly square at first attempt. Two tie wraps supplied with diffuser. This is a superb quality product.