External Thread and nut are left hand threads. Internal thread is FPT. For use with tanks having a wall thickness of 1/16" to 1/2". Material - Body and Nut are either Nylon (N) or Polypropylene (P) Friction washer is Polyethylene, sealing washer is either Buna (B) or EPDM (E). Nylon, Buna, and Polyethylene used in manufactruing are FDA approved grades.