Mr O-Ring 245 Viton O-Ring 90A Durometer, 4-3/8 in ID (Pack of 10)

In this review the Mr O-Ring 245 Viton O-Ring is evaluated for technicians, maintenance pros and hobbyists who need a heat- and chemical-resistant seal in repeatable sizes. The bottom line: this pack of ten 90A durometer Viton o-rings is best for applications exposed to high temperatures, fuels or aggressive fluids because its fluorocarbon compound withstands up to 232C and resists petroleum, diesel, biodiesel blends and many solvents. The review focuses on fit, material performance and typical use cases where the combination of the 4-3/8 in nominal inner diameter and the 1/8 in cross-section matter most.

Key Features

• Material: The Viton (FKM) compound provides outstanding resistance to high temperature, ozone and a wide range of chemicals, making these o-rings suitable for harsh environments.
• Temperature range: Rated from -26C (-15F) to 232C (450F), they hold seals under high heat and low temperature service without rapid degradation.
• Size accuracy: Nominal and actual dimensions are closely matched (4-3/8 in nominal ID, actual 4.359 in ID) so repeatable fit is achieved for parts designed to AS568 size equivalents.
• Durometer: The 90A hardness gives a firmer seal for static and some dynamic applications where compression set and extrusion resistance are priorities.
• Pack quantity: Sold as a pack of 10, the set provides spare parts for routine maintenance or multiple assemblies without needing to reorder frequently.
• Versatility: Performs well with petroleum, diesel, biodiesel blends, methanol/ethanol blends, silicone oils and in high vacuum applications, expanding usable service scenarios.

Who It's For

This o-ring pack is aimed at maintenance engineers, industrial mechanics and DIYers who work with fuel systems, hydraulic components, pumps or ovens where high temperature resistance and chemical compatibility are required. The 90A hardness and Viton formulation make it especially useful when exposure to mineral oils, fuels and aromatic solvents is expected.

Those who need softer, more flexible seals for low-pressure static sealing or very tight dynamic rotary seals might prefer a lower durometer or a different elastomer. If you need metric-size inventory or very soft rubber for cushioning, this specific 90A Viton with 1/8 in cross-section is not the ideal choice.

Pros & Cons

Pros

• Excellent chemical and temperature resistance due to the fluorocarbon Viton compound.
• Accurate actual dimensions (4.359 in ID, 4.637 in OD, 0.139 in CS) for predictable fit in AS568-equivalent housings.
• 90A durometer delivers good extrusion resistance and durability in demanding service.
• Pack of 10 provides convenient spares for maintenance cycles.

Cons

• 90A hardness may be too stiff for applications requiring very soft or highly conforming seals.
• Not specified for specialty chemicals outside the common solvents and fuels listed, so verify compatibility for unusual media.

Specifications

Material	Viton (FKM) fluorocarbon rubber
Durometer	90A
Nominal dimensions	4-3/8 in ID, 4-5/8 in OD, 1/8 in CS
Actual dimensions	4.359 in ID, 4.637 in OD, 0.139 in CS
Metric dimensions	110.72 mm ID, 117.78 mm OD, 3.53 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	10 o-rings

Our Verdict

For anyone needing a durable, heat- and chemical-resistant seal in a common AS568-equivalent size, this 245 Viton 90A o-ring pack is a reliable, cost-effective choice. It delivers accurate sizing, broad fluid compatibility and long service life for fuel, oil and high-temperature applications, though those needing softer seals should consider a lower durometer alternative.

Frequently Asked Questions

Are these o-rings compatible with diesel and biodiesel?
Yes, the Viton compound is rated for petroleum products including diesel and blends with biodiesel as noted in the product description.

Will the 90A hardness work for dynamic seals?
90A can be used for some dynamic applications but is firmer; verify movement, speed and extrusion gaps before selecting for rotary shafts.

Do these match AS568 sizes?
The o-rings are offered to meet AS568-defined sizes and the actual dimensions are provided to confirm fit.