Mr O-Ring 266 Viton O-Ring 90A, 8in ID 8-1/4in OD Pack of 10 - Durable

In this review the Mr O-Ring 266 Viton O-Ring (pack of 10) is evaluated for technicians, maintenance crews, and DIYers who need a reliable high-temperature seal. The bottom line: this 90A durometer Viton o-ring stands out for its wide temperature tolerance and chemical resistance, making it a practical choice where petroleum, fuels, oils or exposure to ozone and weathering are expected. The review focuses on real-world sealing performance, dimensional accuracy, and where this size fits common hydraulic and plumbing repairs.

Key Features

• Material: Made from Viton (fluorocarbon rubber FKM) for excellent resistance to fuels, oils and many solvents.
• Temperature range: Rated from -26C (-15F) to 232C (450F), allowing use in high temperature environments without rapid degradation.
• Durometer: The 90A hardness provides a firm sealing surface that resists extrusion while still compressing to form a reliable seal.
• Dimensions: Nominal 8in ID, 8-1/4in OD and 1/8in cross-section with actual dimensions close to nominal for predictable fit in standard glands.
• Chemical compatibility: Performs well with petroleum, diesel and biodiesel blends, methanol or ethanol blends, mineral and silicone oils, and many acids and solvents.
• Pack quantity: Supplied as a pack of 10, convenient for multiple repairs or stocking spares.

Who It's For

This o-ring is aimed at professionals and experienced hobbyists who work on hydraulic systems, fuel systems, pumps and industrial equipment where exposure to high temperature and aggressive fluids is common. It is also useful for facilities maintenance teams needing a standard AS568-compatible size in bulk.

Those looking for a softer seal for low-pressure or delicate elastomeric applications, or who require food-grade or FDA-approved elastomers, should look elsewhere. This product is optimized for chemical and temperature resistance rather than very low durometer compression sealing.

Pros & Cons

Pros

• Excellent high temperature and chemical resistance suitable for fuels, oils and many solvents.
• 90A durometer gives a durable, extrusion-resistant seal in demanding service.
• Actual dimensions closely match nominal sizes, simplifying replacement in standard glands.
• Pack of 10 offers good value for maintenance stocking and repeat repairs.

Cons

• Firmer 90A hardness may not seal as well in very low-pressure or delicate flange applications that need a softer material.
• Not intended for applications requiring specific food-grade or medical certifications.

Specifications

Brand	Mr O-Ring
Material	Viton (FKM)
Durometer	90A
Nominal dimensions	8in ID, 8-1/4in OD, 1/8in CS
Actual dimensions	7.984in ID, 8.262in OD, 0.139in CS
Metric dimensions	202.79 mm ID, 209.85 mm OD, 3.53 mm CS
Temperature range	-26C (-15F) to 232C (450F)

Our Verdict

The Mr O-Ring 266 Viton o-ring pack is a solid choice for industrial and maintenance uses where high temperature and chemical resistance matter. With accurate dimensions, a durable 90A hardness and the versatility of Viton, it delivers dependable sealing for fuel, oil and high-temperature systems, making the pack of 10 a practical value for professionals who need reliable spares.

Frequently Asked Questions

Is this o-ring compatible with diesel and biodiesel?
Yes, the Viton formulation is rated for diesel and biodiesel blends and performs well with petroleum products.

Will the 90A hardness seal well in low-pressure fittings?
It seals reliably in many applications but the firmer 90A durometer may be less forgiving than softer elastomers for very low-pressure or irregular surfaces.

Does the size conform to AS568 standards?
Yes, the product is manufactured to meet the AS568 size definitions for the listed nominal dimensions.