This 16" (406) diam. roof drain is fitted with a combination flashing clamp and gravel stop that creates a watertight, puncture free bond with roofing materials. All parts are constructed of 14 Gauge Type 304 stainless steel for a very long, corrosion free service life. This drain is engineered for installation in flat roofs where substantial precipitation is anticipated. It is available with 02" (50), 03" (75), 04" (100), 06" (150) or 08" (200) down outlets for connection to the drainage system.