391 Viton O-Ring 75A, 22 in ID - Durable Chemical & Fuel Seal

In this review the 391 Viton O-ring is evaluated as a straightforward replacement seal for applications that demand chemical and heat resistance. The bottom line: this pack of five 75A durometer O-rings is best for technicians and hobbyists who need reliable, compact seals for fuel systems, hydraulic fittings, and equipment exposed to high temperatures. Its main selling point is material performance - made from Viton fluorocarbon elastomer, these O-rings resist a wide range of fuels and chemicals while maintaining form and sealing ability across a large temperature span.

Key Features

• Material: Viton fluorocarbon elastomer offers broad chemical and fuel resistance for demanding service environments.
• Temperature range: Rated for use from -15 degrees F to 400 degrees F, making it suitable for high-heat and low-temperature applications.
• Hardness: 75A durometer provides a balance of resilience and penetration resistance for durable sealing under pressure.
• Shape and fit: Round cross-section seals between overlapping cylindrical surfaces to prevent leaks in common plumbing and fuel fixtures.
• Standards: Manufactured to AS568A sizes, which simplifies replacement and compatibility with many standard fittings.
• Pack quantity: Supplied as a pack of five, giving you spares for maintenance or multiple installations.

Who It's For

The 391 Viton O-ring is well suited to maintenance technicians, gunsmiths, and DIYers who need an O-ring that handles fuels, aromatic and aliphatic hydrocarbons, silicone oils, and many chlorinated solvents without rapid degradation. It is a practical choice for replacing worn seals in fuel bottles, firearm barrel interfaces, and vacuum equipment.

Those who should look elsewhere include users requiring compatibility with strong alkalis, amines, glycol-based brake fluids, or super-heated steam, since Viton is vulnerable to those chemistries. If a softer or very low-temperature compound is required, a different elastomer may be a better fit.

Pros & Cons

Pros

• Excellent resistance to fuels and many chemicals, so it holds up where other elastomers fail.
• Wide usable temperature range from -15 degrees F to 400 degrees F for versatile service.
• 75A durometer gives a durable, leak-resistant seal that customers report fits well in common replacement roles.
• Sold in packs of five, offering value and spare parts for routine maintenance.

Cons

• Not compatible with low molecular organic acids, some amines, alkalis, and glycol-based brake fluids, which limits use in some chemical systems.
• 75A hardness may be firmer than desired for extremely delicate sealing interfaces needing softer material.

Specifications

Material	Viton (fluorocarbon elastomer)
Color	Black
Inner diameter	22 in
Outer diameter	22-3/8 in
Cross-section width	3/16 in
Durometer	75A
Temperature range	-15 degrees F to 400 degrees F

Our Verdict

The 391 Viton O-ring is a practical, value-minded choice for anyone needing a resilient seal compatible with a broad range of fuels and chemicals. For routine maintenance on fuel bottles, pneumatic fittings, or high-heat fixtures it delivers durable leak resistance and sensible longevity, provided the excluded chemistries are avoided.

Frequently Asked Questions

Will this O-ring work with gasoline and diesel?
Yes, Viton is compatible with many fuels, including aromatic and aliphatic hydrocarbons, making it suitable for gasoline and diesel applications.

Can I use these O-rings with brake fluid?
No, Viton is not recommended for glycol-based brake fluids; those fluids can degrade Viton over time.

Are these standard sizes easy to replace?
Yes, these O-rings conform to AS568A sizing conventions, so they fit many common standard fittings and replacement roles.