431 Viton O-Ring 75A Durometer, 5-1/4 in ID - Pack of 10

In this review the 431 Viton O-ring is evaluated as a practical sealing choice for technicians, hobbyists, and maintenance professionals who need a durable, chemical-resistant replacement O-ring. The bottom line is that this pack of ten provides reliable heat and fuel resistance at a sensible price, making it a good buy when compatibility with hydrocarbons and high temperatures is the priority. The reviewer found the 75A hardness and round cross-section give a predictable seal in cylindrical fittings and small pumps without the fuss of custom fabrication.

Key Features

• Material: Made of Viton fluorocarbon elastomer to resist many fuels and chemicals for longer service life.
• Temperature range: Rated from -15 degrees F to 400 degrees F to handle hot engine or industrial environments without rapid degradation.
• Hardness: 75A durometer provides firm resistance to penetration while allowing enough compression for a reliable seal.
• Shape and fit: Round cross-section designed to form a secure seal between overlapping cylindrical surfaces in pumps and fittings.
• Compatibility: Suitable with aromatic and aliphatic hydrocarbons, silicone oil, and high vacuum conditions for a range of applications.
• Standards: Produced to meet the AS568A sizing standard so it fits common grooves and housings that accept that spec.

Who It's For

This pack is best for mechanics, gunsmiths, and field technicians who replace seals in fuel systems, suppressors, or hydraulic fittings and need a material with proven resistance to fuels and heat. The pack of ten means small shops or DIYers won't run out during repairs or modifications.

Those who need resistance to strong bases, ammonia gas, glycol-based brake fluids, or sustained super-heated steam should look for alternative elastomers, since Viton is vulnerable to these media. Also, if extreme low-temperature flexibility below the specified range is required, a different compound may be better.

Pros & Cons

Pros

• Durable chemical and fuel resistance makes these O-rings suitable for tough service environments.
• Wide operating temperature range supports both hot and some cold applications without rapid failure.
• Consistent 75A hardness and AS568A sizing give predictable fit and sealing performance in standard grooves.

Cons

• Not compatible with low molecular organic acids, amines, strong alkalis or glycol-based brake fluids, which limits use in some automotive systems.
• Stiffer 75A hardness can be less forgiving in very low-temperature or ultra-delicate sealing needs.

Specifications

Material	Viton (fluorocarbon elastomer)
Durometer	75A
Inner diameter (ID)	5-1/4 in
Outer diameter (OD)	5-3/4 in
Cross-section width	1/4 in
Color	Black
Standards	Meets AS568A sizing

Our Verdict

The 431 Viton O-ring pack is a sensible buy for anyone replacing seals exposed to fuels, aromatic or aliphatic hydrocarbons, and heat where durability matters. With standard sizing and a durable 75A durometer, it offers good value for routine maintenance and specialized assemblies, but users should verify media compatibility when acids, amines, or glycol fluids are present.

Frequently Asked Questions

Are these O-rings suitable for fuel system use?
Yes; Viton is compatible with many fuels and aromatic hydrocarbons, making these suitable for many fuel system seal replacements.

What temperatures can they withstand?
They are rated for continuous use from -15 degrees F to 400 degrees F, covering most automotive and industrial conditions short of super-heated steam exposure.

Do they fit standard grooves?
Yes; the O-rings meet AS568A sizing conventions and the dimensions stated should fit standard grooves that accept that series.