Mr O-Ring 263 Viton O-Ring 90A Durometer, 7-1/4 in ID (Pack of 10)

In this review the reviewer looks at the Mr O-Ring 263 Viton O-Ring pack to decide whether it is the practical choice for demanding sealing tasks. The bottom line: this pack of ten 90A durometer Viton o-rings is aimed at technicians, mechanics and maintenance teams who need durable, heat- and chemical-resistant seals in a standard AS568-compatible size. Its strongest selling point is the proven performance of Viton (FKM) across high temperature and petroleum-based environments, making it a reliable replacement part for systems exposed to fuels, oils, solvents and ozone.

Key Features

• Material: Viton (FKM) provides exceptional resistance to high temperatures, ozone and many organic chemicals for long service life.
• Hardness: The 90A durometer delivers a firm seal that resists extrusion while maintaining flexibility needed for static and some dynamic seals.
• Temperature range: Rated from -26C (-15F) to 232C (450F), it covers most automotive, industrial and HVAC temperature demands.
• Dimensions: Nominal 7-1/4 in ID by 7-1/2 in OD with 1/8 in cross-section provides a close match to AS568 size 263 applications.
• Pack quantity: Sold as a pack of 10, it is convenient for routine maintenance and small projects where multiple identical seals are required.
• Chemical compatibility: Performs well in petroleum products, fuels, biodiesel blends, mineral and silicone oils, and many solvents for wide application use.

Who It's For

The Mr O-Ring 263 Viton is best suited to workshops, fleet maintenance shops and serious DIYers who regularly service engines, pumps, or fluid-handling equipment exposed to fuels, hydraulic fluids or high heat. Its resistance to methanol or ethanol blends and strong acids makes it useful where standard nitrile o-rings would fail.

Those who should look elsewhere include users needing extreme low-temperature flexibility below -26C or who require a softer durometer for delicate dynamic sealing; likewise, applications that demand food-grade or potable-water certification should consider specifically certified elastomers instead.

Pros & Cons

Pros

• High-temperature and chemical resistance of Viton reduces seal failures in hot or solvent-exposed environments.
• 90A durometer offers robust resistance to extrusion and wear for many industrial sealing tasks.
• Pack of 10 provides good value for maintenance cycles and replacements.
• Manufactured to AS568 size standards for straightforward replacement in standard housings.

Cons

• Higher durometer and Viton material can be stiffer than softer o-rings, which may not suit some low-pressure dynamic seals.
• No food-grade or potable-water certification specified, so not ideal for those regulated uses.

Specifications

Material	Viton (FKM)
Durometer	90A
Nominal dimensions	7-1/4 in ID x 7-1/2 in OD x 1/8 in CS
Actual dimensions	7.234 in ID x 7.512 in OD x 0.139 in CS
Metric dimensions	183.74 mm ID x 190.80 mm OD x 3.53 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack size	10 o-rings

Our Verdict

The Mr O-Ring 263 Viton 90A pack is a pragmatic, cost-effective choice for professionals and serious hobbyists who need reliable seals that withstand heat, fuels and aggressive chemicals. It is good value when a firm, long-lasting o-ring is required for AS568-compatible housings, though projects needing softer materials or specific food-grade approvals should consider alternative compounds.

Frequently Asked Questions

Are these o-rings compatible with fuel and biodiesel?
Yes, Viton (FKM) is formulated to perform well in petroleum products, diesel, and blends including biodiesel and alcohol blends in many cases.

Do these match AS568 size standards?
Yes, the product meets AS568 size definitions and the nominal and actual dimensions are listed to help confirm compatibility.

Can they be used at very low temperatures?
The rated low end is -26C (-15F); for environments colder than that, a different elastomer with better low-temperature flexibility is recommended.