2.5mm X 9mm (NBR) Buna-N 70 Duro Metric O-Ring

Metric Buna-N (Nitrile) O-Rings 70 Duro Black

When you need reliable, cost-effective sealing, Buna-N 70 Duro O-Rings are the industry's most trusted solution. Known for their durability and versatility, these general-purpose O-Rings deliver excellent resistance to petroleum-based oils, fuels, and hydraulic fluids, making them ideal for pumps, valves, motors, and cylinders across hydraulic and pneumatic systems. With strong tensile strength and abrasion resistance, they reduce downtime, extend equipment life, and perform consistently in demanding environments.

Operating temperature: -40° to +250°F (-40° to +121°C)

Key Advantages

• Exceptional resistance to petroleum oils, hydrocarbon fuels, and LP gases
• Strong tensile strength and abrasion resistance for longer service life
• Performs well in water, dilute acids, silicone oils/greases, and ethylene glycol fluids
• Reliable, cost-effective choice for more than 50% of O-Ring sealing applications

Recommended Uses

• General purpose sealing
• Hydraulic and pneumatic equipment
• Petroleum oils and gasoline
• Silicone lubricants and greases
• Cold water and ethylene glycol-based fluids
• Di-ester base lubricants (MIL-L-7808)

Not Recommended For

• Ozone, sunlight, and weather exposure
• Halogenated hydrocarbons (e.g., carbon tetrachloride, trichloroethylene)
• Nitro hydrocarbons (e.g., nitrobenzene, aniline)
• Ketones (e.g., MEK, acetone)
• Phosphate ester hydraulic fluids (e.g., Skydrol, Fyrquel)
• Strong acids and automotive brake fluids

O-Ring Compound Information

• Material: Nitrile (Buna-N), sulfur-cured
• Hardness: 70 Shore A
• Color: Black
• FDA: No
• ASTM D2000-99 Grade: M2BG714 B14 EA14 EF11 EF21 EO14 EO34 Z1 (TR10 = -31.9°C)
• Meets or exceeds popular Nitrile compound standards: N674-70, N100-70, 7507, B46-70, 4200-70, H14327, 4700-70, 366Y

O-Ring Shelf Life & Storage for NBR O-Rings

The long-term reliability of NBR O-Rings depends heavily on proper storage. While Buna-N has a recommended shelf life of 15 years under SAE-ARP5316 and ISO 2230, that assumes storage in ideal conditions.

At The O-Ring Store, every NBR O-Ring is stored in a dedicated, climate-controlled facility at a stable 72°F year-round. Products are protected from natural light, UV, ozone, excess humidity, and physical stress. Each O-Ring remains sealed in its original packaging until it is shipped, preserving its elasticity and performance.

Why this matters to you: Nitrile rubber deteriorates rapidly when exposed to sunlight, ozone, or poor storage conditions. Even brief exposure outside of a controlled environment can shorten shelf life, leading to hardening, cracking, or permanent deformation.

For this reason, we cannot accept returns once Buna-N  O-Rings leave our facility. A Buna-N O-Ring can begin to deteriorate in just a few hours of direct sunlight. In fact, an O-Ring left on a sunny workbench over a single weekend may already show signs of hardening, surface cracking, or loss of flexibility. Once outside our controlled storage environment, we cannot guarantee how the product was handled, and even brief UV exposure can compromise its long-term reliability. By maintaining strict storage practices, we ensure that every NBR O-Ring you purchase arrives in fresh, reliable condition, ready for immediate use.

Best Practices for Storing NBR O-Rings

If you plan to store O-Rings after delivery, follow these guidelines:

• Keep below 77°F (25°C) in a cool, dry place
• Maintain humidity under 75%
• Protect from direct sunlight and artificial UV sources
• Avoid ozone exposure (from motors, welders, electrical equipment)
• Store without tension or compression (never hang or stack under weight)
• Keep sealed in original packaging until use

Customer Benefit: Every Buna-N O-Ring from The O-Ring Store is kept under ISO 9001:2015 certified storage practices. That means when it arrives, you€™re getting the longest usable life and most reliable performance possible, not an O-Ring that's already aged on someone else's shelf.