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Viton Back-up Rings

Contoured Back-Ups are routinely produced in a 90 durometer Viton-FKM. This provides sufficient elasticity to permit stretching over the major diameter of a piston and then snapping back into the gland groove cut into the piston.  90 durometer has sufficient hardness to resist extrusion of the softer elastomeric O-Ring performing the actual sealing function against the high pressure liquid or gas.

- 000 Series O-rings 0.070" ±0.003" - .045" Thick
- 100 Series O-rings 0.103" ±0.003" - .045" Thick
- 200 Series O-rings 0.139" ±0.004" - .040" Thick
- 300 Series O-rings 0.210" ±0.005" - .060" Thick
- 400 Series O-rings 0.275" ±0.006" - .096" Thick

NOTE: Sizes (Dash No.) corresponds to standard O-ring numbers.


What are the most common O-ring compounds?

We stock O-Rings in over 20 different compounds and durometers the following six are the standard rubber materials in a range of durometers (Shore A) hardness to satisfy practically any service condition:

Buna-N O-Rings / Nitrile O-Rings / NBR: Nitrile (Buna-N) is the most widely used elastomer due to its excellent resistance to petroleum products, operating temperature range (-40°F to +257°F) and one of the best performance-to-cost values. It's an ideal material for aerospace, automotive, propane and natural gas applications. Special Hydrogenated Nitrile (HNBR) compounds can improve resistance to direct ozone, sunlight, and weather exposure while increasing temperature range to +300°F.
AS-568 Buna-N O-Rings | Metric Buna-N O-Rings

Viton® O-Rings / FKM: Fluorocarbon (Viton®) exhibits exceptional resistance to chemicals, oils, temperature extremes (-13°F to +446°F), low compression set, low gas permeability and excellent aging characteristics. Applications include: aircraft engines, automotive fuel handling systems, and chemical processing industries. FKM is also suitable for high vacuum applications. It is not recommended for exposure to ketones, alkalis, and Skydrol® fluids. Custom compounds are available with improved chemical and low temperature resistance.
AS-568 Viton® O-Rings | Metric Viton® O-Rings

Ethylene-Propylene / EPDM O-Rings: EPDM has outstanding resistance to heat, water and steam, alkali, mild acidic and oxygenated solvents, ozone, and sunlight (-40ºF to +275ºF); but it is not recommended for gasoline, petroleum oil and grease, and hydrocarbon environments. This popular rubber compound is usually the first choice for low torque drive belt applications.
AS-568 EPDM O-Rings | Metric EPDM O-Rings

Silicone O-Rings / VMQ: In the Silicone family, you will find compounds which are superior as static seals in extreme temperature conditions. Standard compounds handle operating temperatures -85º to +400ºF. Silicone compounds are popular in food and medical applications because they are very clean and do not impart odor or taste. Special Phenyl silicones can be used down to -148°F.
AS-568 Silicone O-Rings | Metric Silicone O-Rings

Neoprene® O-Rings / CR: Neoprene (-40º to +250ºF) is reasonably priced and features good resistance to petroleum oils, ozone, sunlight and oxygen aging, relatively low compression set, good resilience and outstanding physical toughness. It is the preferred sealing material for the refrigeration industry because of its resistance to ammonia and Freon®.
AS-568 Neoprene® O-Rings



O-Rings