243 Viton O-Ring 90A, 4-1/8 in ID (Pack of 10) - High Temp Seal

In this review the reviewer looks at the 243 Viton O-Ring in a 10-pack and finds it best suited for demanding sealing tasks where chemical and heat resistance matter most. Designed with a 90A durometer and Viton fluorocarbon compound, this o-ring is intended for mechanics, technicians, and maintenance professionals who need a compact, reliable seal that tolerates fuels, oils and high temperatures. The single biggest reason to buy is durability: these rings combine a wide operating temperature range with strong resistance to petroleum products and many solvents, making them a dependable choice for industrial and automotive repairs.

Key Features

• Material: Viton FKM construction provides excellent resistance to high temperature, ozone and a broad set of chemicals for long service life.
• Hardness: The 90A durometer gives a firm seal that resists extrusion and maintains shape under pressure in many dynamic and static applications.
• Size accuracy: Nominal and actual dimensions are listed so installers can match existing grooves or housings with confidence.
• Temperature range: Rated from -26C to 232C (-15F to 450F), suitable for high-heat environments and engine compartments.
• Chemical compatibility: Performs well with petroleum fuels, diesel, biodiesel blends, mineral oils, silicone greases and many organic solvents.
• Pack size: Supplied as a pack of 10, useful for small repair shops or maintenance kits where multiple spare seals are needed.

Who It's For

This o-ring is aimed at professionals and experienced DIYers who work with fuel systems, hydraulic components or high-temperature equipment and need a seal that handles fuels, oils and solvents without swelling or rapid degradation. The firmness and Viton compound make it especially relevant for automotive fuel injector seals, pump housings and industrial valves.

Casual users seeking a generic household o-ring or those needing very soft elastomers for low-pressure plumbing should look elsewhere; silicone or nitrile materials with lower durometer values can be a better match for simple, low-temperature sealing tasks.

Pros & Cons

Pros

• Excellent chemical and high-temperature resistance from the fluorocarbon Viton compound.
• Consistent 90A hardness that resists extrusion and holds shape under load.
• Pack of 10 gives spare parts on hand for routine maintenance or multiple installations.
• Actual metric and imperial dimensions are specified to aid correct replacement.

Cons

• Higher durometer means it may feel stiff in low-temperature or low-pressure sealing where softer elastomers seal better.
• Viton can be more expensive than common nitrile alternatives, so it may be overkill for simple household uses.

Specifications

Material	Viton (FKM)
Durometer	90A
Nominal ID	4-1/8 in
Nominal OD	4-3/8 in
Nominal CS	1/8 in
Actual Dimensions	4.109 in ID, 4.387 in OD, 0.139 in CS
Temperature Range	-26C (-15F) to 232C (450F)

Our Verdict

The 243 Viton O-Ring 90A in a pack of 10 is a strong choice for technicians and maintenance professionals who need a small, reliable seal that withstands fuels, oils and high temperatures. Its firm 90A hardness and accurate sizing make it a practical, cost-effective option for industrial and automotive sealing tasks where durability and chemical resistance matter most.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, the Viton FKM compound is formulated to perform well with petroleum fuels, diesel and common fuel blends.

What are the exact dimensions to expect?
Nominally the ring is 4-1/8 in ID, 4-3/8 in OD and 1/8 in cross-section; actual measured sizes are 4.109 in ID, 4.387 in OD and 0.139 in CS.

Can these rings be used at very high temperatures?
Yes, they are rated up to 232C (450F), making them suitable for many high-temperature sealing applications.