This coupling is a class 3000 forged stainless steel 304/304L pipe fitting with female National Pipe Taper (NPT) threads on both ends for connecting and extending pipes of same sizes going in the same direction. This class 3000 coupling has been forged for durability and is made from stainless steel 304/304L for corrosion resistance. Class is a standard relating to tolerance, construction, dimension, and wall thickness, but it is not a direct measurement of maximum working pressure.