R134A Refrigerant Resistant O-Rings


R134A (1,1,1,2-Tetrafluoroethane) is a refrigerant commonly used in automotive air conditioning. During service these O-Rings will often need replaced. HNBR is an O-Ring material that is resistant to this refrigerant. HNBR is most commonly seen in a green color that makes it easily identifiable. Other applications you would see this combination of R134A and HNBR are airsoft propellant, propellant for delivery of pharmaceuticals, and as a dielectric gas. HNBR is a readily available O-Ring material in AS568 sizes from The O-Ring Store.

Automotive A/C 200 Piece HNBR O-ring Kit


Skydrol Resistant O-Rings


Skydol is a fire resistant hydraulic fluid manufactured by Eastman Aviation Solutions for the aviation industry. This hydraulic fluid is incompatible with many plastics, paints, and most O-Ring materials. The two O-Ring materials that are compatible with Skydrol are EPDM and FFKM. EPDM is the general purpose O-Ring material for phosphate ester based hydraulic fluids such as Skydrol. FFKM will be used for critical applications involving these types of fluids. The O-Ring Store stocks both of these compounds in AS568 and metric sizes.

Link: Skydrol Resistant EPDM O-Rings

Link: Skydrol Resistant FFKM O-Rings

Methyl Ethyl Ketone (MEK) Resistant O-Rings


Methyl Ethyl Ketone, also known as MEK, is a commonly used liquid solvent, plastic welding agent, and polymerization catalyst. Many O-Ring compounds are not serviceable for applications involving MEK. Most standard compounds will have significant swelling and material degradation occur when in contact. The O-Ring Store stocks three compounds that are compatible with Methyl Ethyl Ketone.

Compatible Compounds:

EPDM (Ethylene Propylene Diene Monomer): EPDM is a readily available material and is the most cost effective of MEK resistant O-Ring compounds. It will be the go-to in general purpose applications involving MEK. The O-Ring Store stocks both standard AS568 and metric sizes in this material.

Viton Extreme ETP: Viton Extreme is a fluorocarbon compound that has increased chemical resistance in comparison to standard FKM. Viton ETP will perform well in both static and dynamic applications under MEK exposure. It will perform with little to no volume change, and in temperatures up to 482°F.

FFKM Perfluoroelastomer (Kalrez, Simriz, ect.): FFKM is a premium elastomer with the widest chemical and solvent compatibility available. It will perform well in most applications involving MEK. FFKM is the best material choice for critical applications involving MEK.


If you have any questions involving these materials, or your application, feel free to Contact Us!


Vulcanized O-Rings from The O-Ring Store


Example of a 1/2″ cross-section being vulcanized.

A vulcanized O-Ring is an O-Ring made from vulcanized O-Ring cord stock. The vulcanization process creates a strong and durable bond, making it suitable for a variety of applications. Vulcanized O-Rings are a more readily available and cost effective solution to having large custom molded O-Rings made. The O-Ring Store stocks and is tooled to vulcanize many cross-sections in both metric and standard sizes.  Vulcanized O-Rings are available 6 inches (150mm) inside diameter and above from The O-Ring Store.

When to consider a vulcanized O-Ring:

  • When the size you need is unavailable or has a long lead time.
  • When the O-Ring you need is too large to be molded.
  • When factory minimum is too high.
  • Test or prototype quantity on a large size you would like to test before ordering a production quantity.
  • When your cross-section is unavailable in a molded O-Ring.
  • Large diameter O-Rings or large cross-sections O-Rings.

Available Materials for Vulcanized O-Rings:

Link to vulcanized O-Rings: Vulcanized O-Rings

High Temperature O-Ring Applications


Not all high temperature O-Ring applications require the same O-Ring compounds. Some materials react differently to certain types of heat. In this blog we will go over which compounds will perform well in each common high heat environment.

Silicone – Vinyl-meth-silicone VMQ

Silicone is often what most customers assume is the go-to material for a high temperature O-Ring. Silicone is also FDA compliant and non contaminating, so you see if often in applications involving food handling, as well as medical devices. Not recommended for dynamic or abrasive environments, or gasses due to high permeability.

Viton – Fluorocarbon FKM

Often known as Viton,  fluorocarbon O-Ring materials exhibit great high heat resistance to petroleum and fuel products. Because of this, it is the most common O-Ring among the automotive industry. Standard fluorocarbon compounds are not suitable for applications involving super heated water or steam.

EPDM – Ethylene-Propylene

EPDM is the go-to elastomer for hot water and steam applications. It often seen in water processing equipment, industrial steamers, appliances, automotive cooling systems, pressure washers, and marine equipment. EPDM is not suitable for any applications involving petroleum based products.

Fluorosilicone – FVMQ

Fluorosilicone is great for static sealing of fuels up to +392°F. Because of Its great temperature range and fuel resistance it is widely used in aerospace applications. It is also seen in automotive fuel applications for more extreme fuel applications.  It still has the physical properties of silicone, so it is limited to static sealing applications.

Teflon – PTFE

Teflon is a non-elasted thermoplastic with a wide operating temperature range (-100°F to +500°F). It is virtually chemically inert, and has a very low coefficient of friction. Teflon is often seen in chemical processing, or extreme environment applications. Tenfon is a non-elastic material, but The O-Ring Store also stocks Teflon/PTFE encapsulated Viton or Silicone.


Japanese Industrial Standard O-Rings (JIS B 2401)

The Japanese Industrial standard O-Ring sizes (JIS B 2401) are O-Rings that are unique to Japan’s automotive industry. Often listed as metric O-Rings, these sizes are used in specific automotive applications in Japan. The P series is used for dynamic sealing, G series for static or fixed applications, S series for special sizes, and V series for vacuum flange fittings. At The O-Ring Store, our part numbers will be formatted the same as our standard metric O-Rings, but will have the JIS numbers added to the description. The O-Ring Store keeps good stock of the JIS sizes in both Buna-N 70 Durometer and Viton 75 Durometer.

Part Number Format: N1.50X002.5

Material Prefix (N for Buna-N V for Viton) | Cross-Section | Inside Diameter


See also : O-Ring Materials for Automotive Applications

Automotive O-Ring Materials

automotive-applicationsThe automotive industry uses many O-Rings in many different compounds. Getting the right O-Ring size and material will be the difference between a working product or a product that will fail prematurely. Below we will be listing each compound often seen being used for automotive O-Rings and their typical automotive applications, as well as uncommon applications we come across that work excellent for our customers.

Buna-N (-40°F to +250°F)

Buna Nitrile is the most common O-Ring material across all industries. In automotive it is seen a lot where it is in contact with oils below the temperature of 250°F. It is also resistant to automotive antifreeze, straight gasoline (no ethanol or other additives), and transmission fluids.

Limitations for Buna-N in the automotive industry are temperatures over 250°F, ethanol and other fuel additives, and automotive refrigerants for air conditioning. For standard automotive fuels a Viton or Fluorocarbon O-Ring material is the go-to. The compatible material for automotive refrigerants is HNBR (highly saturated nitrile rubber).

Viton/FKM/Fluorocarbon (-15°F to +400°F)

Viton, also known as FKM or Fluorocarbon, is one of the most common O-Ring materials in the automotive industry due to its resistant to most fluids involved in automotive applications. It will be resistant to all automotive oils up to a temperature of 400°F, and most automotive fuels.

Limitations for this material are automotive refrigerants, and fuels with a high ethanol content or other other additives. To see if this material would be compatible with your type of fuels you may check the chemical compatibility guide. If Viton is not compatible with your type of fuel, you may upgrade to either Viton extreme ETP or Fluorosilicone.

HNBR (-40°F to +300°F)

HNBR, or highly saturated nitrile rubber, is a material similar to Buna-N, but it undergoes a process of being dissolved in a solvent, and then introduced to a catalyst  and hydrogen gas to hydrogenate the nitrile. This allows the HNBR compound to be resistant to automotive refrigerants, and type A steering fluid. It also has a slightly higher temperature resistance of 300°F.

EPDM (-65 to +300°F)

EPDM is the only standard compound that is resistant to automotive brake fluids. That makes it a valuable material to the automotive industry, but it is does not work well for much else. EPDM is not recommended for any petroleum based oils or fuels because it will cause significant swelling and consequently fail in your application.

Fluorosilicone (-76° to +392°F)

Fluorosilicone is a material that combines the temperature range  of silicone and the chemical and fuel resistance of a fluorinated rubber. It is most often seen with aviation fuels and racing fuels. We often see this compound headed to very cold places to replace Viton seals along fuel lines that get too cold for Viton seals. Because of it’s excellent low temperature flexibility, it can seal where no material can.

Fluorosilicone, because it does retain physical properties of silicone, is restricted to static applications only.

Viton Extreme ETP (-8 to +482°F)

Viton Extreme ETP is a compound that is overkill in most automotive applications unless you are using fuels with high alcohol content, or specialty treated fuels. It is a good replacement for a dynamic seal you would normally use fluorosilicone in, but needs to be wear resistant. You may look at the chemical compatibility guide to see if this material is right for you.

If you have any additional questions, or would like to get a quote, feel free to contact us!


1005 Warner Ave, Suite A Lewiston ID 83501 | Phone (208) 413-6377 Fax (208) 413-6719


OEM Startup Assistance

Our OEM Startup Assistance Program


We would like to help you get your project or company started, and create a lifelong business relationship with you and your company. Check out how we can help below!


The O-Ring Store will help you find the right O-Rings or seals for your project. We want to make your procurement of our products to be easy!


Your initial order will be credited 50% up to $500.00 to help you save money while you are in your early development stages.


Using our social media pages, website, or blog, we will market our products using your product, company, or crowdfunding campaign to help create a win-win situation for marketing your product and ours.


Lets get Started!

Click here to get the Startup Assistance Application

Phone (208) 413-6377 Email: oring@theoringstore.com

How To Order O-Rings Online

How To Order O-Rings Online

We like to make getting O-Rings easy. So in this blog post we will go over the steps to get the right O-Ring on our website www.theoringstore.com.

Step 1: The Right Material

There are many places to get the information for choosing your material.

The Chemical Resistance Guide: This is an alphabetical listing of chemicals that you can use check the compatibility of O-Ring materials. It also lists a generic selection guide below the chart on the page for general applications.


Step 2: The Right Size

The O-Ring Size Chart: The O-Ring Size Chart lists all of the AS568 standard O-Rings in their nominal fraction dimensions, their exact dimensions in decimals, and their exact dimensions in millimeters. Once you find the size you need, you can easily navigate to your size in the AS568 O-Ring section. There is also a material selection list with links below the chart.


For metric O-Rings, you will first choose your material, then the cross section, and they will be listed by inside diameters.


Step 3: Checking Out

Once you are have all the O-Rings you need added to your shopping cart, you are ready to check out. Your shopping cart and checkout link will be located at the top right corner of the website. cart

Need Help?:

If you are needing any help at all you can use the live chat/email button that appears at the bottom right of your screen at any time. For any special applications or assistance the contact us page will list emails for the sales team that can help you with any O-Ring or other sealing needs.


Here is a quick video for a visual of how to order O-Rings from our website.

MAX Truck O-Ring kits

MAX Truck O-Ring Assortmentsmax

The MAX Truck O-Ring kit is the kit you need to have on hand if you like having a good supply of O-Rings with the best chance of having the O-Ring size you need. The MAX Truck Kit is the perfect O-Ring kit for service trucks, repair shops, or retail counters. This is a huge assortment with 1,431 pieces covering 81 different sizes of O-Rings.  It is available in Buna-N 70 durometer (90 duro. BOSS and Flange kits), Buna-N 90 Durometer, Viton FKM 75 (90 duro. BOSS and Flange kits), and Viton FKM 90 Durometer. Don’t let your equipment or job be stalled by not having one of these in your inventory!

Click Here to Order Yours!

The MAX Truck O-Ring kit Includes :

  • Box 1 -000 Series 1/16″ CS (sizes and dimensions listed on the AS568 O-Ring Chart) :
  • -006 through -018 25pcs/EA
  • -019 through -022 20pcs/EA
  • -023 through -026 15pcs/EA
  • -028 through -030 15pcs/EA

Box 2 -100 Series 3/32″ CS (sizes and dimensions listed on the AS568 O-Ring Chart) :

  • -109 through -118 25pcs/EA
  • -119 through -120 20pcs/EA
  • -121 through -127 15pcs/EA
  • -128 through -129 10pcs/EA
  • -131 10pcs
  • -133 10pcs
  • -135 5pcs

Box 3 -200 Series 1/8″ CS (sizes and dimensions listed on the AS568 O-Ring Chart) :

  • -210 through 214 20pcs/EA
  • -215 through -222 15pcs/EA
  • -223 through -224 10pcs/EA
  • -226 10pcs
  • -228 10pcs
  • -232 10pcs
  • -236 10pcs

Box4 Boss SAE -900 Series:

  • -903 #3 Fitting 15pcs
  • -904 #4 Fitting 25pcs
  • -906 #6 Fitting 15pcs
  • -907 #7 Fitting 25pcs
  • -908 #8 Fitting 25pcs
  • -910 #10 Fitting 25pcs
  • -912 #12 Fitting 15pcs
  • -916 #16 Fitting 10pcs

Box 5 Flange Seal Kit:

  • Flange Fitting #8 10pcs
  • Flange Fitting #12 10pcs
  • Flange Fitting #16 10pcs
  • Flange Fitting #20 5pcs
  • Flange Fitting #24 5pcs
  • Flange Fitting #32 5pcs