FKM (Fluorocarbon) X-Rings are made from a synthetic rubber compound primarily consisting of vinylidene fluoride (VDF) and hexafluoropropylene (HFP). These seals are known for their excellent resistance to high temperatures, chemicals, oils, and fuels. FKM X-Rings (also known as quad rings) feature a four-lobed cross-section that provides two sealing surfaces, offering superior sealing performance compared to standard O-rings. The 75 Duro (Shore A) hardness offers an optimal balance of flexibility and mechanical strength. FKM X-Rings provide superior mechanical strength, excellent resistance to aging, and high resistance to aggressive media, making them ideal for high-performance applications across automotive, industrial, and aerospace sectors. The X-Ring design also reduces friction and resists spiral twist and roll, extending seal life in dynamic applications.

An X-Ring (also called a Quad Ring) is an elastomeric seal with a four-lobed, X-shaped cross-section instead of the round profile of a standard O-Ring. This geometry creates two distinct sealing lines (four contact lips) rather than a single contact line, and the valleys between the lobes act as small reservoirs.

• Resists Rolling and Twisting — The four-lobed shape engages the groove more positively, preventing the seal from rolling or spiraling during dynamic motion—a common failure mode for O-Rings in reciprocating applications.
• Lower Friction and Smoother Motion — Because the sealing load is distributed across two contact lines, an X-Ring requires less squeeze to seal effectively. This reduces contact stress, friction, and heat generation. Some tests have shown X-Rings requiring as little as 1/5 to 1/6 the torque of an O-Ring in valve applications.
• Built-In Lubrication Pockets — The recesses between the four lobes trap lubricant or process media, maintaining a film at the sealing interface. This helps reduce breakaway friction, stick-slip behavior, and wear over repeated cycles.
• Better Stability and Extrusion Resistance — The wider base and multiple contact points give the seal greater stability within the groove, making it less prone to extrusion under pressure compared to a round O-Ring.
• Protects the Sealing Surface — The mold parting line on an X-Ring is positioned in the valley between lobes, keeping the actual sealing lips free from flash or irregularities that could cause leaks.

X-Rings are most valuable in dynamic applications—reciprocating motion, rotary shafts, frequent start-stop cycles, and directional changes—where O-Rings are prone to twisting or premature wear. For simple, stable static sealing, a standard O-Ring often remains the more cost-effective choice.

Many X-Rings are also designed to fit into standard O-Ring grooves, making them a practical upgrade without requiring hardware redesign.

Seals and gaskets, chemical processing, automotive fuel systems, hydraulic systems, aerospace applications, high-temperature applications, oil and gas industry, extreme environment applications, and dynamic sealing applications where reduced friction and resistance to spiral failure are beneficial.

Ketones, esters, amines, low molecular weight acids, and some high-temperature steam systems.

• Not suitable for low-temperature environments.
• Limited performance in swelling from contact with certain fuels and solvents.
• Not recommended for applications involving polar solvents.
• Not ideal for applications that involve high shear or abrasion conditions.

-20 to 450°F (-29 to 232°C)

FKM X-Ring, Quad Ring, FKM Quad Ring, Viton® X-Ring, Fluorel®, Fluoroelastomer X-Ring, Fluorocarbon Elastomer X-Ring.