This general purpose drain is adjustable on-site to accommodate roofs of any construction between 1-1/4" (32) and 4" (100) thick with up to 2-3/4" (70) of insulation. The combination flange clamp and gravel stop of this 15-1/4" (390) diam. adjustable roof drain spins around a threaded extension sleeve to conform to varying roof thicknesses. The drain body and flange assembly are made of Duco coated cast iron. It is protected by a polyethylene dome strainer.