A PN16 flange rubber gasket is a mechanical seal that's used to join two pipe sections and prevent leaks of gas or liquid. The "PN" in PN16 stands for Pressure Nominale, and indicates that the flange is designed to operate up to 16 bar. 

Here are some things to know about PN16 flange rubber gaskets:

• Material
  They can be made from a variety of materials, including rubber, cork, and non-asbestos fibres. The material used depends on the application, such as the internal conditions of the pipeline and the external environment of the pipe. 
• Types
  PN16 gaskets can be manufactured as IBC gaskets, which sit inside the bolt circle of the flange, or as full faced gaskets, which cover the face of the flange and have bolt holes. 

• Uses
  In addition to preventing leaks, rubber flange gaskets can also be used as a barrier between two objects, such as two metals or chemicals. They can also be used to protect from outside elements.