An O-ring is described by its physical size (inside diameter and cross section), and the material that you have selected as the one that best meets the demands of your application.  Material is usually one from those listed below together with the required hardness.  Other properties will include colour and any special properties such as the material being approved for use in a particular type of service e.g. food processing or drinking water.

The following table lists the most commonly requested materials together with their ISO 1629 abbreviation.

Most designers begin with selecting an O-ring size, as the physical constraints are defined by the housing that their design is based on.  Our advice is to try to select an O-ring size from the BS 1806/AS568A series of sizes as this series of sizes has the broadest and deepest range of available stock.

ISO 1629

M - Group (saturated carbon molecules in main macro-molecule-chain)

ACM

– Polyacrylate Rubber

CSM

– Chlorosulphonated Polyethylene Rubber

EPDM

– Ethylene Propylene Diene Rubber

EPM

– Ethylene Propylene Rubber

FPM

– Fluorocarbon Rubber

FFKM

– Perfluoro Rubber

O - Group (with oxygen molecules in the main macro-molecule chain)

CO

– Epichlorohydrin Rubber

ECO

– Epichlorohydrin Copolymer Rubber

R - Group (unsaturated hydrogen carbon chain)

CR

– Chloroprene Rubber

IIR

– Butyl Rubber

NBR

– Nitrile Butadiene Rubber

NR

– Natural Rubber

SBR

– Styrene Butadiene Rubber

HNBR

– Hydrogenated Nitrile Butadiene Rubber

Q - Group (with Silicone in the main chain)

MFQ

– Fluorosilicone Rubber

VMQ

– Methyl Vinyl Silicone Rubber

U - Group (with carbon, oxygen and nitrogen in the main chain)

AU

– Polyester Urethane

EU

– Polyether Urethane