.625ft Buna-N O-Ring Cord Stock 70A Durometer - 100 ft Spool

In this review the.625' Buna-N O-Ring Cord Stock is presented for technicians, hobbyists, and maintenance crews who need a durable, fuel-resistant sealing cord in bulk. The bottom line: this round 0.625' cord in 70A durometer is best for forming custom O-rings and repairs where resistance to petroleum fluids and abrasion matters most. The reviewer found it straightforward to cut and glue into rings, with reliable thickness and consistent hardness that suits many hydraulic, plumbing, and equipment sealing tasks.

Key Features

• Material: Buna-N (Nitrile, NBR) offers strong compatibility with petroleum-based fluids and many hydraulic fluids for dependable sealing in oil-exposed applications.
• Durometer: The 70A hardness provides a durable balance of flexibility and resilience, making formed O-rings resist compression set while maintaining a tight seal.
• Temperature range: Rated for a wide temperature span, it performs in cold starts and warm operating conditions common to workshop and industrial environments.
• Length and size: Supplied on a 100 ft spool at 0.625' thickness, it gives ample material to produce many custom rings and repairs without frequent reordering.
• Made in USA: Domestic manufacture means consistent quality control and reliable material properties across the spool.

Who It's For

This cord stock is aimed at maintenance technicians, small fabrication shops, and DIYers who need to make replacement O-rings, seal repairs, or custom gaskets for equipment exposed to oils, greases, and many hydraulic fluids. The spool size and material make it particularly useful where multiple or large rings are required.

It is not ideal for applications exposed to ozone, prolonged UV, or solvents such as acetone and certain esters; users needing extreme low-temperature flexibility beyond the listed range or resistance to aggressive polar solvents should consider alternative elastomers.

Pros & Cons

Pros

• Good resistance to petroleum and hydraulic fluids, which helps prevent swelling and loss of seal integrity in oil-exposed systems.
• Durable 70A hardness balances wear resistance and flexibility for long-lasting formed O-rings.
• Long 100 ft spool provides value and reduces downtime for frequent repairs or multiple projects.
• Customers report ease of gluing and good fit when forming replacement rings, making installation straightforward.

Cons

• Sensitivity to ozone, sunlight, and some solvents means it should not be used outdoors or near ozone-generating equipment without protection.
• The cord is specific to applications compatible with Buna-N; it is not the best choice for extreme chemical resistance outside its compatibility list.

Specifications

Our Verdict

The.625' Buna-N cord stock is a practical choice for anyone needing to form reliable O-rings for oil and hydraulic applications; it offers solid durability, good adhesive behavior, and excellent value per foot. For indoor equipment and fluid-exposed seals it is an economical, dependable solution, though users needing ozone or UV resistance should select a different elastomer.

Frequently Asked Questions

Can this cord be glued into O-rings?
Yes; customers report it bonds readily with appropriate rubber adhesives and is easy to form into functional rings.

Is this material compatible with petroleum and hydraulic fluids?
Yes; Buna-N is compatible with many petroleum, HFA, HFB, and HFC fluids, vegetable oil, and aliphatic hydrocarbons.

Can it be used outdoors or near ozone sources?
No; Buna-N is vulnerable to ozone, sunlight, and certain solvents and should be avoided in outdoor or ozone-exposed applications.