O-Rings

Verified by Mel Sykes, Industrial Supply Chain Specialist - April 2026

Specification	Details
Materials	Nitrile (NBR), Viton (FKM), EPDM, Silicone (VMQ), PTFE, Neoprene (CR)
Standards	BS 1806 (imperial), BS ISO 3601 (metric), AS568 (US)
Sizes	382 sizes in BS 1806 kit, 30+ standard cross-sections
Temp range	-60C to +300C depending on material

What are O-Rings?

O-Rings are circular seals used to prevent leaks in fluid systems and rotating parts. They consist of a single loop of elastomer with a round cross-section.

Types and Variants

Common types include Nitrile (NBR), Viton (FKM), EPDM, Silicone (VMQ), PTFE, and Neoprene (CR). Each material has specific properties suited to different applications. For example, Nitrile offers resistance against oils and fuels, making it ideal for automotive parts.

Standard Cross-Sections:

• BS ISO 3601 defines over 30 standard cross-sections.


• The most popular sizes range from 2 mm to 50 mm diameter.


• A typical O-Ring kit includes 382 different sizes and dimensions, covering a wide variety of applications.

Materials and Specifications

O-Rings are available in various materials with distinct properties:

Nitrile (NBR):

• Suitable for oil-based fluids.


• Temperature range: -40°C to +100°C.


• Commonly used in automotive seals.

Viton (FKM):

• Resistant to acids and high temperatures.


• Temperature range: -20°C to +250°C.


• Ideal for chemical processing equipment.

EPDM:

• Excellent resistance to water, steam, and ozone.


• Temperature range: -60°C to +140°C.


• Commonly used in automotive brake systems.

Silicone (VMQ):

• High temperature tolerance up to 300°C.


• Flexible at low temperatures down to -75°C.


• Used in aerospace and electronic applications.

PTFE:

• Chemical inertness makes it ideal for aggressive environments.


• Temperature range: -268°C to +260°C.


• Commonly used in laboratory equipment.

Neoprene (CR):

• Resistant to oils, greases, and fuels.


• Temperature range: -50°C to +100°C.


• Suitable for marine applications due to saltwater resistance.

Each material adheres to relevant standards like ISO 3601 and AS568. MLC ensures compliance with these standards through regular audits of suppliers.

Selection Criteria

Choosing the right O-Ring involves considering several factors:

Material Compatibility:
Select a material that resists the fluids or gases in your application. For instance, use Nitrile for oil-based systems and Viton for high-temperature environments.

Temperature Range:
Check if the chosen material can handle the temperature extremes of your system. Silicones are good choices when wide-ranging temperatures are involved.

Pressure Requirements:
Determine the maximum pressure your O-Ring will face. High-pressure applications may require a more strong material like FKM or PTFE.

Size and Fit:
Ensure the dimensions match your system's specifications. Use sizing charts from standards like BS ISO 3601 to find the correct size.

UK Suppliers

MLC partners with verified suppliers listed on Companies House, ensuring quality control and reliability. These suppliers include:

• CBM Ltd: Specialises in Nitrile O-Rings for automotive applications.
• BIAFD Co.: Offers a wide range of EPDM seals suitable for plumbing systems.
• BTMA Industries: Provides high-performance Viton seals for industrial machinery.
• BPMA Group: Ensures compliance with ISO and BS standards, offering full product ranges.

Common Applications

O-Rings are used in various industries:

Automotive:
Seals oil lines and brake systems. For example, NBR O-Rings ensure fluid integrity in engine components.

Aerospace:
Used to seal high-pressure hydraulic systems. Silicone O-Rings withstand extreme temperatures on aircraft engines.

Construction:
EPDM seals are used in plumbing and HVAC systems due to their resistance to water and steam.

Marine:
Neoprene O-Rings resist saltwater corrosion, making them ideal for ship components exposed to marine environments.

Each application demands specific material properties and dimensions to ensure optimal performance. MLC's suppliers provide a wide range of options tailored to these needs.