Mr O-Ring 333 Viton O-Ring 90A, 2-1/2 in ID - Pack of 10

In this review the Mr O-Ring 333 Viton O-Ring is evaluated for workshop and industrial sealing tasks; the bottom line is that it is a dependable choice for users who need a high-temperature, chemical-resistant seal in a standard AS568 size. Tested as a pack of 10 with a 90A durometer, these black Viton rings suit applications where resistance to fuels, oils and elevated temperatures matters most. The reviewer found the nominal 2-1/2 in ID size and the slightly tighter actual dimensions provide a secure squeeze in typical gland designs, making this pack useful for maintenance shops and hobbyists who value consistency.

Key Features

• Material: FKM Viton construction provides strong resistance to high temperature, ozone and many solvents, so seals last longer in harsh environments.
• Hardness: 90A durometer offers a firm seal that resists extrusion in many static and low-dynamic applications, giving reliable compression set performance.
• Size accuracy: Actual dimensions (2.475 in ID, 2.895 in OD, 0.210 in CS) are close to nominal, which helps fitment in AS568-compatible grooves without excessive adjustment.
• Temperature range: Rated from -26C (-15F) to 232C (450F), allowing use across a wide span of operating conditions from cold starts to high-heat systems.
• Chemical compatibility: Performs well with petroleum fuels, diesel, biodiesel blends, mineral oils and many organic solvents, making it versatile for fuel and hydraulic sealing tasks.
• Pack quantity: Sold as a pack of 10, which is convenient for routine maintenance and replacing multiple seals at once without buying single units.

Who It's For

The Mr O-Ring 333 Viton is best for technicians, mechanics and engineers who need a robust sealing material that endures fuel exposure and elevated temperatures; it is particularly appropriate for fuel system seals, hydraulic fittings and equipment exposed to ozone or weathering. The pack of 10 suits shops that perform regular maintenance or users replacing several seals in assemblies.

Those who should look elsewhere include applications requiring extreme flexibility at very low temperatures below -26C or where a softer durometer is preferred for dynamic rotary shafts. Also choose a different elastomer if compatibility with certain aggressive amine-based chemicals or steam service is required.

Pros & Cons

Pros

• Excellent chemical and high-temperature resistance for fuel and oil-exposed seals.
• Consistent dimensions and AS568 sizing make replacements straightforward.
• 90A hardness reduces extrusion and retains shape under compression.
• Pack of 10 provides good value for maintenance tasks.

Cons

• Relatively firm 90A durometer may be too stiff for some low-pressure dynamic shaft seals.
• Not suitable for certain highly reactive chemicals or steam applications.

Specifications

Material	Viton (FKM)
Durometer	90A
Nominal dimensions	2-1/2 in ID, 2-7/8 in OD, 3/16 in CS
Actual dimensions	2.475 in ID, 2.895 in OD, 0.210 in CS
Metric dimensions	62.87 mm ID, 73.53 mm OD, 5.33 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack size	10 o-rings

Our Verdict

The Mr O-Ring 333 Viton 90A in this pack of 10 is a smart buy for maintenance professionals and hobbyists who need a durable, chemically resistant seal in a common AS568 size. It delivers dependable temperature and fuel resistance with consistent dimensions, making it good value for replacing fuel and oil-exposed seals where a firmer durometer is acceptable.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, the Viton formulation is suitable for petroleum fuels, diesel and many blended fuels including biodiesel blends.

Will the 90A hardness work for dynamic shaft seals?
The 90A durometer is fairly firm and is best for static or low-dynamic sealing; softer durometers are preferable for high-speed rotary shafts.

Do these meet a standard size?
Yes, the rings conform to common AS568 size standards with nominal and actual dimensions noted for fitment.