Mr O-Ring 343 Viton O-Ring 90A Durometer Pack of 10 - High Temp Seal

In this review the Mr O-Ring 343 Viton O-Ring (pack of 10) is assessed for professionals and DIYers who need a durable, high-temperature seal. The bottom line: this Viton (FKM) o-ring is best for applications exposed to fuels, mineral oils, high heat and harsh environments because of its 90A durometer hardness and broad temperature range. Practical measurements and AS568 sizing make it straightforward to replace common seals, and the 10-pack offers immediate spare parts without guessing compatibility.

Key Features

• Material: Viton (FKM) construction provides excellent resistance to fuels, oils and many solvents, so it holds up in aggressive chemical environments.
• Hardness: The 90A durometer gives a firm, reliable seal that resists extrusion and deformation under pressure for consistent performance.
• Temperature range: Rated from -26C (-15F) to 232C (450F), allowing use in both cold storage and very high temperature air systems.
• Dimensional accuracy: Nominal and actual dimensions are provided so users can match by fit: 3-3/4 in ID nominal with actual 3.725 in ID for proper replacements.
• Pack quantity: Sold as a pack of 10, which is convenient for maintenance shops or repeated repairs without reordering.
• Standards: Sized to meet AS568 standards, simplifying selection for common industry sealing tasks.

Who It's For

This o-ring is aimed at mechanics, maintenance technicians and hobbyists who service fuel systems, hydraulic components, or equipment exposed to high temperatures and oils. The chemical resistance of Viton makes it suitable for diesel, biodiesel blends, petroleum products and many organic solvents where nitrile or EPDM would degrade.

Those who should look elsewhere include users needing extremely soft, low-durometer seals for delicate compression or where low friction is critical, and applications requiring FDA food-grade certification or very low-temperature service below -26C.

Pros & Cons

Pros

• Excellent chemical and high temperature resistance from the Viton FKM compound.
• Firm 90A hardness resists extrusion and maintains seal under pressure.
• Clear nominal and actual dimensions make it easy to match replacements without guesswork.
• Pack of 10 gives immediate spares for maintenance tasks, reducing downtime.

Cons

• 90A hardness may be too stiff for applications that require a softer seal or low-friction movement.
• Not specified as food-grade, so it is not ideal for direct food or potable water contact.

Specifications

Product	343 Viton O-Ring, pack of 10
Material	Viton (FKM)
Durometer	90A
Nominal dimensions	3-3/4 in ID, 4-1/8 in OD, 3/16 in CS
Actual dimensions	3.725 in ID, 4.145 in OD, 0.210 in CS
Metric dimensions	94.62 mm ID, 105.28 mm OD, 5.33 mm CS
Temperature range	-26C (-15F) to 232C (450F)

Our Verdict

The Mr O-Ring 343 Viton 90A pack of 10 is a solid choice for anyone needing a reliable, high-temperature seal resistant to fuels and oils; it is good value for workshops and technicians who require durable replacements and quick spares. Choose this for chemical-exposed and high-heat sealing tasks, but consider a softer compound if you need more flexibility or food-grade approval.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, the Viton FKM compound resists petroleum products, diesel and common fuel blends, making them suitable for those applications.

Do the sizes follow an industry standard?
Yes, the rings are sized to AS568 standards and the listing provides both nominal and actual dimensions to ensure a proper fit.

Can these be used in very low temperature environments?
They are rated down to -26C (-15F); for colder service a different low-temperature compound would be recommended.