Small Parts S70.157/25 Silicone O-Ring Cord 0.157in - High Temp Seal

In this review the Small Parts S70.157/25 silicone O-ring cord stock is evaluated for technicians, hobbyists, and maintenance pros who need a reliable, high-temperature sealing material. The bottom line: this red, 70A durometer silicone cord delivers predictable elasticity and excellent resistance to ozone, weather, and many oils across a very wide temperature range, making it a practical choice when rebuilding seals or cutting custom O-rings. The review focuses on real-world handling, temperature performance, and chemical compatibility to help decide if it fits a given sealing task.

Key Features

• Material: Silicone construction offers stable elasticity and flexibility for a variety of sealing and cushioning uses.
• Temperature range: Rated for extreme temperatures, it performs from very low cold to very high heat for demanding environments.
• Durometer: The 70A hardness provides a balanced firmness that is easy to compress for reliable sealing without being too soft.
• Cross-section and length: Supplied as a round cord in a 25 ft piece so users can cut custom O-rings and gaskets as needed.
• Chemical resistance: Resists ozone, weathering, detergents, salt water, and many oils, making it suitable for outdoor and marine exposures.
• Made in the U.S.A.: Domestic manufacture means consistent quality control for industrial and maintenance applications.

Who It's For

This silicone O-ring cord is best for mechanics, HVAC technicians, laboratory technicians, and DIYers who need to fabricate custom seals that will see a wide temperature span or exposure to ozone and weather. It suits repairs on equipment where non-petroleum brake fluids, certain hydraulic fluids, or vegetable and animal oils are present.

Users who need resistance to strong acids, aromatic hydrocarbons like benzene, or long-term water/steam exposure above 250 degrees F should look for alternative elastomers, since silicone has known vulnerabilities in those specific conditions.

Pros & Cons

Pros

• Good functionality: customers report the cord works well for custom O-rings and has reliable sealing performance.
• High quality: consistent 70A durometer and round cross-section make cutting predictable rings.
• Wide temperature tolerance: handles very low to very high temperatures useful for varied environments.
• Chemical and weather resistance: performs well against ozone, detergents, salt water, and many oils.

Cons

• Limited chemical resistance: not suitable for strong acids, certain solvents, or aromatic hydrocarbons.
• Mechanical wear: silicone is more vulnerable to abrasion and long-term steam above 250 degrees F than some other rubbers.

Specifications

Brand	Mr O-Ring
Material	Silicone
Durometer	70A
Cross-section	Round cord, 0.157 in thickness
Length	25 ft piece
Temperature range	Approximately -76 F (-60 C) to 437 F (225 C)
Origin	Made in the U.S.A.

Our Verdict

The Small Parts S70.157/25 silicone O-ring cord is a practical, good-value choice for anyone fabricating seals that must resist weathering, ozone, and a range of oils while enduring wide temperature swings. It is not the best choice where abrasion, strong solvents, or high-temperature steam exposure exceed silicone's limits, but for general maintenance, HVAC, and many industrial applications it offers dependable performance and predictable handling.

Frequently Asked Questions

Can I cut custom O-rings from this cord?
Yes. The 0.157 in round cord and consistent 70A hardness make it straightforward to cut and join custom O-rings and small gaskets.

Will this cord resist engine oil and hydraulic fluids?
Silicone resists many engine and transmission oils and certain hydraulic fluids, but check specific fluid compatibility for long-term exposure to petroleum-based fuels.

Is this suitable for steam and high-temperature water applications?
Silicone performs up to high temperatures but is vulnerable to water and steam exposure above about 250 degrees F, so avoid prolonged steam service at higher temperatures.