O-rings

The 'O' ring is a simple, versatile and economical devise with a vast range of uses, the most common of which is a static seal replacing a gasket or sealing washer. It can also be used as a single or double acting dynamic seal. It can be used to seal radially in both internal and external positions as well as axially on its faces.
The most commonly used material is nitrile 70 shore. This elastomer can seal the majority of normal applications including water, oil, petrol and most mild chemicals up to 100 degrees C, and 1500 psi.
Consideration must be given for low temperatures (below 130 degrees C), high temperatures, high pressures, hazardous chemicals and solvents, and for use with food, portable water and various gas standards.
A commonly overlooked requirement is for ozone, weathering etc where EPDM or silicone perform better than Nitrile in most circumstances.