251 Viton O-Ring 75A Durometer, 5-1/8 in ID - Pack of 25

In this review the 251 Viton O-ring is evaluated for technicians, hobbyists, and maintenance professionals who need reliable seals for fuel, chemical, and high-heat applications. The bottom line: it is a practical replacement O-ring that stands out for chemical and temperature resistance, making it a solid choice when durability under stress is the primary concern. Most users will buy it for dependable leak resistance and longevity rather than aesthetic fitment, since its main strength is material performance rather than cosmetic finish.

Key Features

• Material: Viton fluorocarbon elastomer offers broad resistance to fuels, aromatic and aliphatic hydrocarbons, and many solvents, so it holds up where many other elastomers fail.
• Temperature range: Rated from -15 degrees F to 400 degrees F, allowing use in both cold storage and high-heat environments without rapid degradation.
• Durometer: 75A hardness provides a balance of resilience and penetration resistance, which helps maintain sealing force under compression and repeated cycles.
• Form factor: Round cross-section and standard AS568A sizing mean it creates a reliable seal between overlapping cylindrical surfaces in common plumbing and hydraulic joints.
• Chemical compatibility: Suitable for non-flammable hydraulic fuels, silicone oils, and many chlorinated and aromatic hydrocarbons, widening possible applications.
• Quantity: Pack of 25 gives spares for maintenance shops or multiple replacement tasks without frequent reordering.

Who It's For

This O-ring is aimed at maintenance techs, firearm and suppressor owners who need replacement seals, and industrial users dealing with fuels and solvents where heat resistance and chemical compatibility matter. Repair shops and field technicians will appreciate the pack size and standardized sizing for common fittings.

It is less suited for applications exposed to low molecular organic acids, ammonia gas, strong alkalis, amines, glycol-based brake fluids, or super-heated steam, where alternative elastomers should be considered. For purely cosmetic or low-demand household uses, a cheaper general-purpose elastomer may be sufficient.

Pros & Cons

Pros

• Excellent chemical and heat resistance makes it reliable for fuel and solvent environments.
• Standard AS568A sizing and round cross-section ensure consistent sealing performance in cylindrical joints.
• Pack of 25 provides value for frequent maintenance or multiple installations.
• Customers report good fit and leak resistance in common replacements like fuel bottle seals and barrel seals.

Cons

• Not compatible with some acids, amines, alkalis, and glycol-based brake fluids, so compatibility checks are required.
• Higher durometer and specialty material make it overkill for simple low-temperature, non-chemical household seals.

Specifications

Material	Viton (fluorocarbon elastomer)
Color	Black
Inner diameter (ID)	5-1/8 in
Outer diameter (OD)	5-3/8 in
Width	1/8 in
Durometer	75A
Standards	Meets AS568A

Our Verdict

The 251 Viton O-ring is a practical, cost-effective option for professionals and hobbyists who need a durable seal that resists heat and common fuels. Buy it if you need long-lasting leak resistance and chemical compatibility; skip it only when exposed to known incompatible chemicals or when a soft, low-temperature elastomer is required.

Frequently Asked Questions

Will this O-ring handle gasoline and diesel?
Yes, Viton is compatible with many fuels and aromatic or aliphatic hydrocarbons, making it suitable for fuel-related seals.

Is this O-ring suitable for high-temperature use?
Yes, it is rated for use up to 400 degrees F, so it performs well in many high-heat environments.

Can this replace common AS568 sizes?
Yes, it meets AS568A sizing standards and is suitable for many standard cylindrical sealing applications that use those sizes.