Mr O-Ring 359 Viton O-Ring 90A Durometer, 5-3/4 in ID Pack of 10

In this review the Mr O-Ring 359 Viton O-Ring is assessed for mechanics, hobbyists, and industrial users who need a durable sealing solution that resists fuels and high temperatures. The bottom line: this pack of ten 90A durometer Viton o-rings is best for applications where chemical resistance and thermal stability matter most, offering the right balance of firmness and elasticity for repeated sealing under harsh conditions.

Key Features

• Material: Fluorocarbon rubber (Viton/FKM) delivers strong resistance to fuels, oils, solvents and many chemicals so seals last longer in aggressive environments.
• Temperature range: Rated from -26C to 232C (-15F to 450F), providing dependable performance across very low to very high operating temperatures.
• Durometer hardness: At 90A durometer the o-ring holds its shape under compression, reducing extrusion and improving long-term sealing in static and some dynamic uses.
• Dimensions: Nominal 5-3/4 in ID, 6-1/8 in OD and 3/16 in cross-section with actual dimensions close to 5.725 in ID and 6.145 in OD for reliable fit in standard AS568 sized grooves.
• Pack quantity: Sold as a pack of 10 which is convenient for repeat maintenance tasks or stocking common replacement sizes.
• Application range: Performs well with petroleum fuels, biodiesel blends, silicone oils, high vacuum and ozone exposure, extending usable service life in varied systems.

Who It's For

This product is aimed at technicians, machine shops, marine and automotive repair shops, and enthusiasts who require a robust seal that tolerates fuels, high temperatures and aggressive chemicals. The 90A hardness and Viton compound make it suitable for static seals or slow-moving shafts where chemical compatibility is critical.

Those needing softer, more flexible o-rings for low-pressure dynamic seals or food-grade silicone alternatives should look elsewhere, as the 90A Viton compound prioritizes chemical and heat resistance over extreme elasticity.

Pros & Cons

Pros

• Excellent chemical resistance to fuels, oils and many solvents, so seals endure harsh service conditions.
• High temperature capability to 232C (450F) allows use in engines and heated systems without rapid degradation.
• Consistent 90A hardness provides firm sealing and reduces extrusion in many groove designs.
• Pack of 10 offers good value for maintenance and replacement needs.

Cons

• Higher durometer means less flexibility for very low-pressure dynamic sealing where softer compounds perform better.
• Viton is not suitable for certain specialized chemistries not listed in the product description, so verify compatibility for exotic media.

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)
Quantity	Pack of 10

Our Verdict

The Mr O-Ring 359 Viton 90A o-ring is a practical choice for anyone needing a heat- and chemical-resistant seal in automotive, industrial or marine systems; the pack of ten and AS568-compliant sizing make it good value for maintenance shops and serious hobbyists who prioritize longevity and compatibility over extreme softness.

Frequently Asked Questions

Are these o-rings suitable for fuel exposure?
Yes, the Viton compound is specified to perform well with petroleum products, fuel blends and biodiesel mixes.

Do they meet standard sizing?
They meet AS568 size definitions with nominal and actual dimensions provided for reliable fit.

Can they be used for high temperature applications?
Yes, they are rated to 232C (450F) for high temperature sealing tasks.