X-Rings & Quad Rings (4-Lobe Seals)

Bi-directional sealing with lower friction and longer life than conventional O-rings

Overview

X-Rings — also known as Quad Rings or four-lobe seals — feature a four-lobed cross-section that provides two sealing surfaces on each side of the groove. This unique geometry offers several advantages over standard round O-rings: lower friction, reduced compression set, better resistance to spiral failure, and the ability to seal bi-directionally in dynamic applications. We manufacture X-Rings in NBR, FKM, EPDM, and VMQ (Silicone) to match AS568 and ISO 3601 groove dimensions. Because X-Rings occupy the same groove width as O-rings, they are often used as drop-in upgrades to improve seal life without changing gland design.

Advantages Over Round O-Rings

Lower Friction

The four-lobe design reduces contact area, cutting friction by 20–40% compared to round O-rings. Ideal for reciprocating dynamic seals.

Best for: Pneumatic cylinders, hydraulic rams, valves

Bi-Directional Sealing

Two sealing lips on each side provide reliable sealing in applications where pressure direction alternates or is uncertain.

Best for: Double-acting cylinders, oscillating valves, rotary unions

Spiral Failure Resistance

The stable cross-section resists twisting and rolling in the groove — the primary cause of spiral failure in round O-rings.

Best for: Rod seals, piston seals, high-stroke applications

Longer Service Life

Less heat generation and better lubricant retention extend seal life in continuous dynamic service.

Best for: Production machinery, automation equipment, mobile hydraulics

Materials

Material	Properties	Best For
NBR X-Rings	-40°C to +120°C, excellent oil and fuel resistance, low cost	General hydraulics, pneumatics, fuel systems
FKM X-Rings	-20°C to +200°C, superior chemical and heat resistance	High-temperature hydraulics, chemical processing, aerospace
EPDM X-Rings	-50°C to +150°C, excellent water, steam and ozone resistance	Water systems, HVAC, food and beverage processing
VMQ (Silicone) X-Rings	-60°C to +230°C, FDA grades available, extreme temperature flexibility	Medical devices, food equipment, cryogenic and high-heat static seals

Sizing

X-Rings are dimensioned by inside diameter and cross-sectional width, using the same groove design as standard O-rings. We supply standard sizes to match AS568 and ISO 3601 series, plus custom dimensions.

AS568 Series

• 1.78mm (CS)
• 2.62mm (CS)
• 3.53mm (CS)
• 5.33mm (CS)
• 6.99mm (CS)

ISO 3601 / Metric

• 1.80mm
• 2.65mm
• 3.55mm
• 5.30mm
• 7.00mm

Custom

• Any ID and CS manufactured to drawing

Frequently Asked Questions

What is the difference between an X-Ring and a Quad Ring?

They are the same product. X-Ring and Quad Ring are trade names for seals with a four-lobed cross-section. The terms are used interchangeably in the sealing industry.

Can I use an X-Ring in a standard O-ring groove?

Yes. X-Rings are designed to fit in standard O-ring grooves without changing gland dimensions. Always verify groove width and depth match the specific X-Ring size chart, as squeeze requirements may differ slightly from round O-rings.

When should I choose an X-Ring over a round O-ring?

Choose an X-Ring for dynamic applications where lower friction, longer life, or resistance to spiral failure is important. They are also preferred in double-acting cylinders where pressure direction alternates.

Do X-Rings cost more than O-rings?

X-Rings typically cost 10–30% more than equivalent O-rings due to the more complex mold geometry. The price difference is often justified by longer service life and reduced maintenance in dynamic applications.

What hardness is standard for X-Rings?

70 Shore A is the most common hardness for dynamic X-Rings. Softer compounds (50–60 Shore A) are available for low-pressure or fragile housings, while 90 Shore A is used for high-pressure extrusion resistance.