Mr O-Ring 359 Viton O-Ring 90A Durometer - Pack of 5

In this review the Mr O-Ring 359 Viton O-Ring is assessed for workshop and industrial sealing tasks; it is aimed at technicians, machinists and maintenance professionals who need a durable, high-temperature resistant seal. The bottom line: this pack of five 90A durometer Viton o-rings stands out for chemical and heat resistance, making it a reliable choice where petroleum, fuels, silicone oils or high vacuum conditions are present. Reviewers will appreciate the precise nominal and actual dimensions and the broad usable temperature window, which together make it a practical replacement and maintenance stock item.

Key Features

• Material: Fluorocarbon rubber (Viton) provides strong resistance to fuels, mineral oils, hydraulic fluids and many organic solvents, so seals last longer in aggressive environments.
• Hardness: The 90A durometer balances firmness and elasticity, giving consistent sealing under compression and repeated cycling.
• Dimensions: Nominal 5-3/4 in ID, 6-1/8 in OD and 3/16 in cross-section with actual dimensions listed, which helps when matching to existing grooves or fittings.
• Temperature range: Rated from -26C (-15F) to 232C (450F), allowing use from cold storage to high-temperature process lines without rapid degradation.
• Chemical compatibility: Performs well with petroleum products, methanol or ethanol blends, diesel or biodiesel, silicone oils, and strong acids, expanding its use in varied service media.
• Pack size: Supplied as a pack of five, useful for routine maintenance or multi-point assembly jobs to reduce downtime.

Who It's For

The Mr O-Ring 359 Viton O-Ring is best for professionals maintaining engines, pumps, valves and hydraulic systems where exposure to fuels, oils or high temperatures is routine. Its 90A hardness and Viton compound make it a good fit for industrial maintenance shops, marine applications and HVAC systems that see chemical contact and elevated heat.

It is less appropriate for low-cost consumer projects that never see fuel or high temperature, or for applications that require extremely soft, low-durometer seals for delicate compression; users needing very large custom sizes should look for molded seals rather than AS568-style o-rings.

Pros & Cons

Pros

• Excellent chemical and heat resistance ensures long service life in aggressive media.
• Covers precise nominal and actual dimensions, simplifying direct replacements without guesswork.
• 90A durometer offers a durable seal under repeated compression and mechanical cycling.
• Pack of five gives immediate spare parts for maintenance tasks.

Cons

• Higher durometer means it is stiffer than softer o-rings and may not suit applications needing very soft sealing elements.
• Viton compounds are specialized and typically cost more than general-purpose elastomers.

Specifications

Material	Viton (Fluorocarbon rubber, FKM)
Durometer	90A
Nominal dimensions	5-3/4 in ID, 6-1/8 in OD, 3/16 in CS
Actual dimensions	5.725 in ID, 6.145 in OD, 0.210 in CS
Metric dimensions	145.42 mm ID, 156.08 mm OD, 5.33 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	5 o-rings

Our Verdict

The Mr O-Ring 359 Viton O-Ring is a solid, value-minded choice for professionals who need a resilient seal that tolerates fuels, oils and high temperatures. Its clear dimensioning, 90A hardness and Viton composition make it a dependable replacement part for industrial maintenance and repair. Buy it if you require chemical compatibility and thermal stability; consider softer elastomers only if your application needs a much lower durometer.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, Viton is resistant to petroleum products and works with gasoline, diesel and many fuel blends including biodiesel.

Can they be used at high temperatures?
Yes, they are rated for continuous use up to 232C (450F), suitable for many high-temperature sealing points.

Is the pack quantity suitable for maintenance?
The pack of five makes it convenient for routine replacement or multi-point servicing without immediate reordering.