The 50mm brass flanged outlet M thread is made from brass and used to connect the tank to pipes and pumps. A quality outlet is important as the seal in the tank wall will ensure a trouble free operation for many years.
The outlet comes with a threaded backing ring and most importantly a quality seal which prevents leaks and provides a long life to the tank and fitting.
The installation is important and matching the whole size with the outlet is critical to a leak free tank.