O-rings are simple in shape and easily stretched for assembly and available in a choice of sizes and materials.

They are the most versatile and economic form of seal on the market and are accepted by engineers as an essential item in hydraulic and pneumatic equipment.

These o-rings have excellent resistance to weathering, water and steam, and have a high performance in castor and some phosphate ester based fluids. It is functional in both low and high temperatures.

This material is good for sealing both boiling water and steam, making them perfect for central heating systems. They should never be used in contact with mineral based fluids or di-ester based lubricants due to excess swell and deterioration.

This material is popular due to its excellent high temperature capability, and resistance to hydraulic oils, petrol and other chemicals.

These o-rings can only handle low temperatures to -15 degrees Celsius. Some grades of Viton can accommodate lower temperatures but this functionality does come at an increased cost.

Silicone rubber o-rings are ideal for high temperatures and are widely used in the medical and food production field due to its non-toxicity.

However, they have a poor tensile strength, poor tear and abrasion resistance, high permeation of gasses, and poor resistance to mineral fluids.

Silicone rubber can be chemically modified to become fluorosilicone, which gives it reasonable oil and fuel resistance combined with high and low temperature capabilities.

They still have poor strength like the silicone rubber, and are an expensive option usually limited to specialised fields such as aerospace.

Kalrez is considered to be the best material for o-rings. It resists over 1800 different chemicals and offers the high temperature stability of PTFE (327 degrees Celsius).

It is used in highly aggressive chemical processing, semiconductor wafer processing, pharmaceutical, oil and gas recovery, aerospace and petroleum applications.