.313 in Silicone O-Ring Cord Stock 70A - Red, 25 ft

In this review the.313 in silicone O-ring cord stock is examined for workshop and maintenance use where a durable, temperature-resistant sealing material is required. The bottom line: this red, 70A durometer silicone cord is best for users who need a reliable round-section sealant that tolerates wide temperature swings and many chemicals. The reviewer found it particularly useful for custom O-ring fabrication and repair because it combines predictable hardness with broad chemical resistance, and the 25 ft length is practical for multiple small jobs.

Key Features

• Material: Silicone construction provides resistance to ozone, weather and many detergents, making it suitable for outdoor and exposed applications.
• Temperature range: Rated for extremely low and high temperatures so it maintains flexibility from cold starts to high-heat environments.
• Durometer: 70A hardness strikes a balance between compressibility and durability for many static sealing tasks.
• Cross section: Rounded cord stock lets a user cut and form custom O-rings or seals to fit nonstandard grooves and housings.
• Length: Supplied as a 25 ft piece, providing enough material for multiple replacement seals or prototypes.
• Origin: Made in the U S A, which can matter for consistent manufacturing and material traceability.

Who It's For

This cord stock is aimed at technicians, hobbyists, and maintenance pros who build or replace O-rings and need a silicone option that handles a wide temperature band and resists environmental exposure. It is especially useful where resistance to ozone, seawater, detergents, and certain oils is required.

Those who need petroleum fuel resistance, extended steam exposure above 250 degrees F, or high abrasion resistance should consider alternative elastomers; silicone excels for temperature range and weatherability but is not ideal for heavy mechanical wear or strong aromatic solvents.

Pros & Cons

Pros

• Broad temperature capability delivers reliable sealing from very low to very high operating temperatures.
• Good chemical resistance to ozone, salt water, detergents and many oils for outdoor and marine uses.
• 70A durometer offers a useful middle ground between soft and stiff seals for many static applications.
• 25 ft length and round cross-section make it convenient for fabricating multiple custom O-rings.

Cons

• Silicone is vulnerable to certain aromatic and chlorinated hydrocarbons and can wear faster under heavy mechanical abrasion.
• Performance with water and steam degrades above 250 degrees F, limiting some high-steam applications.

Specifications

Material	Silicone
Cross section	Round cord
Thickness	0.313 in (5/16 in)
Durometer	70A
Length	25 ft
Temperature range	-76 F to 437 F (approx -60 C to 225 C)
Origin	Made in the U S A

Our Verdict

This.313 in silicone O-ring cord stock is a practical choice for anyone needing a durable, temperature-tolerant sealing material that is easy to cut and form into custom rings. It represents good value for routine sealing tasks and prototype work where chemical exposure is limited to the fluids silicone resists.

Frequently Asked Questions

Can this cord be used to make replacement O-rings?
Yes. The round 0.313 in cross-section and 70A hardness make it well suited for cutting and splicing into custom O-rings for static seals.

Is this silicone suitable for continuous high-temperature steam?
Not recommended for continuous steam over 250 degrees F, as silicone performance with steam degrades above that temperature.

Will it resist engine oil and marine conditions?
Silicone resists many engine and transmission oils plus salt water and weather, but avoid prolonged contact with aromatic or chlorinated hydrocarbons.