366 Viton O-Ring 75A Durometer 7-1/4in ID 7-5/8in OD - Durable Seal

In this review the author tests the 366 Viton O-ring as a practical replacement seal for industrial and consumer equipment; the bottom line is that it is a straightforward, durable O-ring best suited to applications that need chemical and heat resistance. The reviewer found the size and finish make it an easy swap for fuel bottle interfaces and barrel seals, and the material properties mean it handles hot environments and many fuels without swelling or rapid degradation. It is not a specialty compound for every chemical, but for most fuel, oil and high-temperature sealing needs this pack is a sensible choice.

Key Features

• Material: Viton fluorocarbon elastomer offers excellent resistance to fuels, aromatic and aliphatic hydrocarbons, and many chemicals, keeping seals intact under exposure.
• Temperature range: Rated from -15 degrees F to 400 degrees F, it can be used where heat resistance and thermal stability are required.
• Size and shape: The round cross-section with a 7-1/4in ID and 7-5/8in OD provides a reliable seal between overlapping cylindrical surfaces common in plumbing and equipment repairs.
• Hardness: 75A shore durometer gives a firm resistance to penetration while remaining flexible enough for compression sealing.
• Standards: Manufactured to AS568A size standards, making it interchangeable with common replacement O-rings and easier to match to existing parts.
• Pack quantity: Supplied as a pack of 10 which reduces repeat ordering and is useful for multiple maintenance tasks.

Who It's For

This O-ring is aimed at technicians, hobbyists, and equipment owners who need a robust replacement seal for fuel systems, hydraulic fittings, vacuum components, and other cylindrical joints exposed to heat or hydrocarbon-based fluids. It is particularly useful when matching AS568A sizes for common industrial and consumer parts.

It is less suitable for environments that expose seals to strong alkalis, ammonia gas, low molecular weight organic acids, or glycol-based brake fluids, as Viton is known to be vulnerable to those media; systems using those fluids should seek a compound specifically rated for that chemistry.

Pros & Cons

Pros

• Good compatibility with fuels and many hydrocarbons so it holds up in fuel bottle and barrel-seal applications.
• Wide operating temperature range allows reliable sealing from cold starts to high-heat conditions.
• 75A durometer balances durability and flexibility, reducing extrusion while maintaining a tight seal.
• Sold in a pack of 10, offering value for routine maintenance and multiple replacements.

Cons

• Not suitable for exposure to ammonia, strong alkalis, certain brake fluids, or super-heated steam, limiting its use in some chemical systems.
• The review notes the compound is a firmer 75A feel which may not suit applications needing a very soft squeeze for low-pressure sealing.

Specifications

Our Verdict

The 366 Viton O-ring is a reliable, value-oriented replacement for users who need heat and hydrocarbon resistance in cylindrical seal joints; its AS568A sizing and pack quantity make it practical for maintenance shops and enthusiasts. Buy it if your application avoids alkalis and the other incompatible fluids noted, as it delivers good durability and leak resistance for the price.

Frequently Asked Questions

Can this O-ring be used with gasoline and diesel?
Yes, Viton is compatible with many fuels and hydrocarbons, so it is suitable for fuel-related sealing in most cases.

Is the size compliant with common O-ring standards?
Yes, this O-ring matches AS568A sizing conventions and is intended to interchange with standard parts of the same dimensions.

Will it resist high-temperature service?
Yes, the compound is rated to 400 degrees F and performs well in high-heat sealing applications within that range.