This is a stainless steel plug with external screws. Casted stainless steel offers superior resistance to load, impact and resistance compared to pressed products. Ball chain available in M39A2, M39A2B, M39A1, M39A1-1. Caution: Please handle with care to avoid scratches or distortion. Materials: Main body: SCS13, nut: nickel-plated brass, rubber plug: NR