Mr O-Ring 347 Viton O-Ring 90A Durometer 4-1/4in ID - Durable Seal

In this review the Mr O-Ring 347 Viton O-Ring is evaluated for technicians and hobbyists who need a reliable, high-temperature seal in petroleum, fuel, or chemical environments. The bottom line: this pack of five 90A durometer Viton o-rings stands out for chemical and heat resistance, making it a practical choice when compatibility with fuels, oils, and solvents is the priority. The reviewer found the nominal and actual dimensions consistent, the hardness right for static and low-dynamic seals, and the listed temperature range useful for demanding applications.

Key Features

• Material: Fluorocarbon rubber (Viton/FKM) provides excellent resistance to petroleum, fuels, many chemicals and solvents, which reduces seal failures in aggressive fluids.
• Durometer: 90A hardness offers a firm seal useful for static and some dynamic sealing tasks while maintaining resilience under load.
• Dimensions: Nominal 4-1/4in ID and 4-5/8in OD with actual dimensions close to nominal, improving fit reliability in standard AS568 applications.
• Temperature range: Rated from -26C (-15F) to 232C (450F), suitable for very high temperature air and many industrial service conditions.
• Pack quantity: Sold as a pack of five, which is convenient for small maintenance jobs or replacement spares without overstocking.
• Standards: Sized to AS568 conventions, simplifying selection for established equipment and replacement parts lists.

Who It's For

The Mr O-Ring 347 Viton is aimed at professionals and experienced DIYers working with fuels, mineral oils, hydraulic fluids, silicone oils, or in environments exposed to ozone and weather. It is a good choice where elevated temperature resistance and chemical compatibility matter, such as engine components, fuel systems, or industrial machinery.

Those who need very soft, low-durometer seals for delicate dynamic shafts or consumers seeking a generic household replacement without specific chemical exposure should consider different materials or hardness. This product is optimized for chemical resistance and heat rather than ultra-low friction dynamic sealing.

Pros & Cons

Pros

• Excellent chemical and high-temperature resistance from the Viton/FKM compound.
• Firm 90A durometer provides durable sealing for static applications and many service conditions.
• Actual dimensions are listed alongside nominal sizes, helping to confirm fit before installation.
• Pack of five offers ready spares for maintenance without bulk purchasing.

Cons

• 90A hardness may be too stiff for some dynamic shaft seals where lower friction is required.
• Not the best choice for extreme low-temperature flexibility below the stated range.

Specifications

Material	Viton (Fluorocarbon rubber, FKM)
Durometer	90A
Nominal ID	4-1/4in
Nominal OD	4-5/8in
Nominal cross-section	3/16in
Actual dimensions	4.225in ID, 4.645in OD, 0.210in CS
Temperature range	-26C (-15F) to 232C (450F)

Our Verdict

The Mr O-Ring 347 Viton 90A is a solid value for anyone needing chemical and heat-resistant seals in petroleum and fuel-exposed systems. Its firm durometer and AS568 sizing make it a practical replacement part for maintenance and repairs, though installers should choose a lower-durometer material when maximum flexibility or low-friction dynamic sealing is required.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, the Viton compound is formulated to perform well in gasoline, diesel and many fuel blends noted in the product description.

Do the actual dimensions differ from the nominal sizes?
The listing provides actual dimensions (4.225in ID, 4.645in OD, 0.210in CS) which are close to the nominal sizes for reliable fit verification.

Can these be used at high temperatures?
Yes, they are rated up to 232C (450F), suitable for many high temperature air and industrial applications.