Mr O-Ring 172 Viton O-Ring 90A Durometer - Pack of 5

In this review the Mr O-Ring 172 Viton O-Ring is presented for technicians and hobbyists who need a durable, high-temperature seal. The bottom line: this pack of five Viton o-rings is best for applications exposed to fuels, oils, high heat and weather because the 90A durometer FKM compound resists petroleum products, ethanol blends and many solvents while maintaining shape across a wide temperature range. The review covers fit, material performance and practical uses so you can decide if these nominal AS568-size rings suit your maintenance needs.

Key Features

• Material: Fluorocarbon rubber (Viton/FKM) provides strong resistance to heat, ozone and a wide range of chemicals for longer seal life.
• Durometer: The 90A hardness keeps the ring stable under compression and offers reliable sealing in static and low-dynamic applications.
• Size accuracy: Nominal 8-1/4 in ID and 8-7/16 in OD with actual dimensions close to spec for predictable fit in AS568 applications.
• Temperature range: Rated from -26C (-15F) to 232C (450F), suitable for very high temperature air and many industrial processes.
• Chemical compatibility: Performs well with petroleum fuels, diesel/biodiesel blends, mineral oils, silicone greases and many organic solvents.
• Pack quantity: Sold as a pack of 5, convenient for small repairs, replacements and keeping spares on hand.

Who It's For

This pack is aimed at mechanics, HVAC technicians, equipment maintainers and DIYers who replace seals on engines, pumps, valves and fittings exposed to fuels, oils or elevated temperatures. The Viton compound and 90A hardness suit static seals and many low-movement joints where chemical resistance and temperature tolerance are priorities.

Those who need extremely soft or flexible o-rings for delicate dynamic seals or food-grade silicone materials should look elsewhere, as this 90A Viton is firmer and formulated for industrial chemical and heat resistance rather than culinary or ultra-low-friction applications.

Pros & Cons

Pros

• High chemical and heat resistance makes these reliable in fuel and oil-exposed systems.
• Accurate actual dimensions (8.237 in ID, 8.443 in OD, 0.103 in CS) aid predictable installation in AS568-sized grooves.
• Pack of five provides immediate spares for maintenance tasks without buying large quantities.
• Unlimited shelf-life means spare rings can be stored long term without degradation concerns.

Cons

• At 90A durometer the rings are relatively firm, which may not be ideal for delicate dynamic seals requiring softer compounds.

Specifications

Brand	Mr O-Ring
Material	Viton (Fluorocarbon rubber, FKM)
Durometer	90A
Nominal dimensions	8-1/4 in ID, 8-7/16 in OD, 3/32 in CS
Actual dimensions	8.237 in ID, 8.443 in OD, 0.103 in CS
Temperature range	-26C (-15F) to 232C (450F)
Pack size	5 rings

Our Verdict

The Mr O-Ring 172 Viton o-ring pack is a practical choice for professionals and DIYers who need a compact supply of chemically resistant, high-temperature seals. Its accurate dimensions, 90A hardness and FKM compound make it good value for fuel systems, pumps and industrial seals where durability and solvent resistance matter.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, the Viton compound performs well with petroleum fuels, diesel and common fuel blends including biodiesel and ethanol blends.

Will the 90A hardness work for dynamic shaft seals?
90A is firmer and best for static or low-dynamic seals; for high-speed shaft seals a softer compound may be preferable.

Do these follow any size standard?
Yes, the rings meet size conventions defined by AS568 and have actual dimensions close to the nominal values for consistent fit.