.750 in Buna-N O-Ring Cord Stock 70A - 10 ft Piece

In this review of the.750 in Buna-N O-Ring Cord Stock the bottom line is simple: this 70A nitrile cord is best for workshop repairs and fluid-resistant seals where durability and chemical compatibility matter. The reviewer found it particularly useful for replacing worn rubber parts and fabricating custom o-rings because the cord is dense, easy to cut, and bonds well with common adhesives. Its temperature range and resistance to petroleum-based fluids make it a practical choice for hydraulic, pneumatic, and general industrial maintenance tasks.

Key Features

• Material: Buna-N (nitrile) offers reliable resistance to petroleum, HFA, HFB, and HFC fluids, making it suitable for many hydraulic and fuel-related uses.
• Hardness: The 70A durometer delivers a balance of flexibility and firmness that holds shape well in seals while still compressing for a tight fit.
• Temperature Range: Rated for a wide working range, the cord performs across common shop temperatures from cold starts to warm operating conditions.
• Made in USA: Domestic manufacture ensures consistent quality and predictable material properties for repeat projects.
• Length and Cross Section: Supplied as a 10 ft piece in a round cross section, it is convenient for cutting multiple custom o-rings or repair segments without seams.

Who It's For

This Buna-N cord is aimed at technicians, machinists, and hobbyists who need a durable, petroleum-resistant sealing material for custom o-rings, tire repairs, or gasket rebuilding. It is also a good fit for maintenance shops that frequently work on hydraulic or pneumatic systems and require consistent hardness and adhesion properties.

Those who need resistance to ozone, sunlight, or aggressive solvents such as acetone and esters should look elsewhere, since Buna-N is vulnerable to ozone, UV exposure, and certain solvents. For high-heat applications above the stated range or for ozone/UV-exposed outdoor seals, a different elastomer is recommended.

Pros & Cons

Pros

• Good chemical compatibility with petroleum and many hydraulic fluids, making it reliable for equipment service.
• Durable 70A hardness that balances wear resistance and sealability for many common applications.
• Easy to cut and glue, so fabricating and repairing custom o-rings is straightforward.
• Sold as a 10 ft piece and made in the USA, providing value and consistent quality.

Cons

• Not suitable for prolonged ozone or UV exposure, so outdoor or electrical-motor environments are a limitation.
• Some customers reported mixed results on exact leak resistance depending on application and fit.

Specifications

Our Verdict

The.750 in Buna-N O-Ring Cord Stock is a practical, cost-effective choice for workshop repairs and fluid-exposed seals where petroleum resistance and a 70A hardness are required. It is particularly good value for those who need a reliable 10 ft supply for multiple custom rings or repairs, but users with ozone, UV, or aggressive solvent exposure should select a different material.

Frequently Asked Questions

Is this cord compatible with hydraulic fluids?
Yes, Buna-N is compatible with many petroleum-based hydraulic fluids including HFA, HFB, and HFC types.

Can it be used outdoors in sunlight?
No, Buna-N is vulnerable to ozone and UV, so it is not recommended for prolonged outdoor sun exposure.

What size and length is supplied?
The product is a round cord 0.750 in thick supplied as a 10 ft piece.