Mr O-Ring 323 Viton O-Ring 90A - 1-5/16 in ID, Pack of 25

In this review the Mr O-Ring 323 Viton O-Ring is assessed for mechanics, fabricators and maintenance buyers who need a small, high-temperature seal in quantity. The bottom line: this pack of 25 provides consistent, high-hardness Viton (FKM) seals rated to 232C/450F that stand up to fuels, oils and harsh environments, making it a practical choice when durability and chemical resistance matter. The review focuses on real-world sealing uses, material performance and whether the listed nominal and actual dimensions match typical installation needs.

Key Features

• Material: Viton FKM construction gives reliable resistance to fuels, mineral oils and many organic solvents for longer seal life.
• Hardness: The 90A durometer offers a firm seal suitable for static and some dynamic applications where a harder cross-section reduces extrusion.
• Temperature range: Rated from -26C to 232C (-15F to 450F), it handles very high temperature air and many high-heat operating environments.
• Pack size: Supplied as a pack of 25, useful for workshops or repeat maintenance jobs without frequent reordering.
• Size accuracy: Nominal AS568 sizing provided with actual dimensions, which helps installers verify fit before assembly.
• Chemical compatibility: Performs well with petroleum, diesel, biodiesel blends, methanol/ethanol blends, silicone greases and some strong acids for versatile use.

Who It's For

These o-rings suit technicians, marine mechanics, and industrial maintenance staff who need compact, high-temperature resistant seals in bulk. The 90A hardness and Viton chemistry are especially appropriate for fuel systems, hydraulic fixtures where mineral oils or fuels are present, and equipment exposed to ozone and weather.

Those needing very soft or low-friction seals for delicate dynamic shafts should look elsewhere; silicone or nitrile in lower durometers may be a better fit. Also, if a specific non-Viton chemical compatibility is required (for example, concentrated ketones not listed), verify compatibility before use.

Pros & Cons

Pros

• Excellent high-temperature tolerance up to 232C for demanding applications.
• Strong chemical resistance to fuels, oils and many organic solvents increases service life in harsh fluids.
• Pack of 25 provides convenience and spare parts economy for routine maintenance.
• Actual dimensions are listed so users can confirm fit against existing grooves and parts.

Cons

• At 90A hardness the o-ring is relatively firm and may not seal as well on very low-compression or irregular surfaces.
• Viton is a premium material and can cost more than general-purpose nitrile for noncritical uses.

Specifications

Material	Viton (FKM)
Durometer	90A
Nominal dimensions	1-5/16 in ID, 1-11/16 in OD, 3/16 in CS
Actual dimensions	1.287 in ID, 1.707 in OD, 0.210 in CS
Metric dimensions	32.69 mm ID, 43.35 mm OD, 5.33 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	25

Our Verdict

The Mr O-Ring 323 Viton 90A in a 25-pack is a solid value for professionals who need durable, chemical-resistant seals that tolerate high heat. It is especially useful where fuel and oil exposure is routine and where consistent dimensions matter for fast maintenance. For low-pressure, ultra-soft sealing needs or cost-sensitive noncritical spares, a different material may be preferable.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, Viton FKM is compatible with petroleum fuels, diesel and many fuel blends listed in the product information.

Will the 90A hardness work on a dynamic shaft seal?
90A is relatively firm and can work in some dynamic applications, but for low-friction dynamic shafts a softer durometer may seal more effectively.

Do the nominal and actual dimensions differ significantly?
The listing provides both nominal AS568-style dimensions and measured actual values so installers can confirm fit before installation.