Mr O-Ring 249 Viton O-Ring 90A Durometer 4-7/8 in ID Pack of 10

In this review the Mr O-Ring 249 Viton O-ring is examined for technicians and maintenance pros who need a resilient, fuel-resistant seal in bulk quantities. The bottom line: this pack of 10 90A durometer Viton o-rings is aimed at applications exposed to high temperatures, fuels and mineral oils where chemical resistance matters most. The reviewer found the nominal 4-7/8 in ID size and the 90A hardness make these rings a practical choice for industrial sealing tasks, especially where compatibility with petroleum, diesel blends, and high heat is required.

Key Features

• Material: Viton (fluorocarbon rubber) delivers strong resistance to high temperature, ozone and many organic solvents, which reduces seal failures in harsh environments.
• Hardness: 90A durometer gives a firm cross-section that resists extrusion and retains shape under compression in demanding mechanical seals.
• Temperature range: Rated from -26C (-15F) to 232C (450F), allowing use across cold starts and very high operating temperatures without rapid degradation.
• Chemical compatibility: Performs well with petroleum products, fuels blended with methanol or ethanol, diesel and biodiesel blends, mineral and silicone oils and greases.
• Dimensions: Nominal 4-7/8 in ID, 5-1/8 in OD, 1/8 in cross-section with precise actual measures for tighter fit in replacement jobs.
• Pack quantity: Supplied as a pack of 10, which suits maintenance shops and repeat service intervals without frequent reordering.

Who It's For

The Mr O-Ring 249 Viton o-ring is best for maintenance technicians, hydraulic and pneumatic service shops, and hobbyists who repair fuel systems, pumps or high-temperature equipment and need a reliable, fuel-resistant seal. Its bulk pack of 10 keeps spare parts on the shelf for recurring service jobs or installations that use standardized AS568 sizes.

Those who should look elsewhere include users needing extreme flexibility at very low temperatures below -26C, or applications that require a softer durometer for delicate, low-force seals; in those cases a silicone or lower-hardness elastomer would be more appropriate.

Pros & Cons

Pros

• Excellent chemical and heat resistance from Viton material reduces replacement frequency in fuel-exposed systems.
• 90A durometer provides firmness against extrusion and is suitable for many industrial sealing tasks.
• Accurate actual dimensions (4.859 in ID, 5.137 in OD, 0.139 in CS) make replacements straightforward for matching AS568 sizes.
• Pack of 10 offers good value for shops and repeat maintenance needs.

Cons

• Higher durometer means it is less supple than softer o-rings, which can be a limitation for low-pressure, delicate sealing surfaces.
• Not suited for extreme cold below the specified -26C range.

Specifications

Brand	Mr O-Ring
Material	Viton (FKM)
Durometer	90A
Nominal dimensions	4-7/8 in ID, 5-1/8 in OD, 1/8 in CS
Actual dimensions	4.859 in ID, 5.137 in OD, 0.139 in CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	10 o-rings

Our Verdict

The Mr O-Ring 249 Viton 90A o-ring is a solid choice for plumbers, mechanics and maintenance teams who need durable, fuel-resistant seals in a common AS568 size. It offers strong chemical and temperature resistance and comes in a practical pack of 10, making it good value for industrial or repeated service use, while users requiring softer or extreme-cold elastomers should consider alternative compounds.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes; the Viton material is rated for petroleum products, gasoline blends and diesel, including some biodiesel blends.

Do the listed sizes match AS568 standards?
Yes; the product is intended to meet AS568 size definitions with nominal and actual dimension data provided for fitting.

How long will these o-rings store on the shelf?
Viton has an unlimited shelf-life when stored properly away from extreme heat and direct sunlight.