266 O-Ring Viton 90A 8in ID 8-1/4in OD Pack of 5 - High Temp Seal

Our review of the 266 O-Ring made of black Viton concludes it is best for users who need a compact, chemical-resistant seal that survives high temperatures and fuels. The single biggest reason to buy is its material: the fluorocarbon elastomer offers broad chemical compatibility and a temperature range from -15 degrees F to 450 degrees F, making it suitable for demanding hydraulic, fuel, and industrial sealing jobs where standard elastomers fail. This review focuses on real-world fit, durability, and whether the AS568A sizing makes installation predictable.

Key Features

• Material: Viton fluorocarbon elastomer gives resistance to fuels, oils, ozone, and weathering for long service life in harsh environments.
• Temperature range: Rated from -15 degrees F to 450 degrees F so it can be used in both low-temperature and high-heat applications without rapid degradation.
• Hardness: 90A durometer provides a firm sealing surface that resists extrusion and maintains shape under pressure.
• Standard sizing: Manufactured to AS568A dimensions so the 8in ID and 8-1/4in OD fit applications expecting Aerospace Size Standard O-rings.
• Cross-section: Round profile creates a reliable seal between cylindrical overlapping surfaces for shafts, housings, and flanged joints.
• Compatibility: Works with a variety of chemicals including silicone oils, aromatic and aliphatic hydrocarbons, and many hydraulic fluids.

Who It's For

This O-ring suits mechanics, fabricators, and maintenance technicians who repair pumps, heaters, valves, and equipment exposed to fuels, solvents, or high temperatures. It is a practical choice for hobbyists who need a reliable seal for custom builds such as pet food vaults or vehicle components where a proven Viton material is required.

Those who should look elsewhere include users needing extreme flexibility at temperatures below -26 degrees C, applications exposed to strong alkalis or amines, or projects that require a softer seal than 90A. If you need a different durometer or a non-Viton compound for specific chemical incompatibilities, choose a different O-ring material.

Pros & Cons

Pros

• Durable Viton compound resists heat, fuels, and many chemicals for long service life.
• AS568A sizing and round cross-section give predictable fit and a reliable seal in cylindrical joints.
• 90A hardness reduces extrusion and maintains sealing under pressure and mechanical wear.
• Pack of 5 offers value for repairs and multiple installations.

Cons

• Stiff 90A durometer may be too hard for applications needing a softer, more compliant seal.
• Viton is vulnerable to low molecular organic acids, ammonia gas, amines, and strong alkalis, limiting use with those chemicals.

Specifications

Material	Viton (fluorocarbon elastomer)
Durometer	90A
Inner diameter	8 in
Outer diameter	8-1/4 in
Cross-section width	1/8 in
Temperature range	-15 degrees F to 450 degrees F (-26 C to 232 C)
Standards	Meets AS568A aerospace size standard

Our Verdict

The 266 Viton O-ring is a dependable choice for professionals and hobbyists who need a high-temperature, chemical-resistant seal in standard AS568A sizes. Its 90A hardness and fluorocarbon compound make it good value for repairs and industrial uses where durability and fuel resistance matter, though users needing extreme low-temperature flexibility or resistance to strong alkalis should consider alternative materials.

Frequently Asked Questions

Will this O-ring work with gasoline and hydraulic fluid?
Yes, Viton is compatible with many fuels and non-flammable hydraulic fluids, making it suitable for those systems.

Is the size standard so replacements are interchangeable?
Yes, the ring is made to AS568A dimensions so it fits ports and grooves designed to that aerospace size standard.

Can it be used at very low temperatures?
It is rated down to -15 degrees F (-26 C); for colder service a different elastomer with better low-temperature flexibility is recommended.