Size -- 1/2" BSP; Center hole diameter: 20mm with 3 bolt holes, the flange can satisfy any home decoration, including various designs Materials -- The industrial malleable cast iron floor threaded flange is made of iron, carbon and silicon alloy composition, high strength, anti-rust treatment, plasticity and machinability Thread -- Pipe thread. National Pipe Taper Thread (NPT). Apply to most iron pipes; Floor flanges are common to use for plumbing. They are used to connect the pipes on your floor or wall Structure -- Frosted surface, anti-rust treatment, threaded alignment, chassis formation The 1/2 inch black floor pipe fittings can be used to make shelves, pipe furniture, drying racks, shelves, lighting retro, and any industrial craft decor