​There is no doubt that O-rings are the simplest and most economical sealing solution to multiple sealing problems. Their design is simple, and they are completely defined by:

• The manufacturing material
• Its internal diameter
• Cross section

The usual materials are usually elastomers, thanks to the good elasticity characteristics they provide. Depending on the fluids to be sealed and the temperature, different synthetic rubbers will be chosen:

• NBR (Nitrile)
• FPM (Viton®)
• VMQ (Silicone)
• EPDM
• FFPM
• …

Alternatively, combined materials, such as a layer of FEP (a fluoropolymer close to PTFE), can be used over an elastomer ring that gives it its elasticity.

Once the material has been chosen, the pressure and the design of the housing will determine the optimum hardness to be used, usually between 70 and 90 ShoreA.

Finally, the material may have to comply with some international regulation or certification such as FDA (Food and Drug Administration), which certifies that the material used is inert and does not pose any risk to the health of the consumer. The pharmaceutical, cosmetics and food industries are particularly sensitive, and gaskets used in machines such as pumps, valves and piping will have to comply with this requirement.

Although O-rings are manufactured mainly by moulding, there are other processes such as extrusion and subsequent vulcanisation or gluing, which allow the rapid manufacture of any diameter without the need for a mould.