342 Viton O-Ring 75A Durometer, 3-5/8 in ID x 4 in OD - Durable Seal

In this review the 342 Viton O-ring is evaluated for technicians, hobbyists, and small shops that need a reliable sealing component resistant to heat and fuels. The bottom line is that this pack of 25 Viton O-rings is best for applications where chemical and high-temperature resistance matter, because the fluorocarbon material and 75A hardness provide long service life in contact with fuels, aromatic hydrocarbons, and many industrial fluids. The reviewer found these rings fit common fittings and bottles while holding up under heat and repeated use.

Key Features

• Viton material: The fluorocarbon elastomer offers strong resistance to fuels, aromatic and aliphatic hydrocarbons, and many chemicals, extending seal life in harsh environments.
• Wide temperature range: Rated from -15 degrees F to 400 degrees F, the o-ring can be used in applications that cycle from cold storage to high heat without rapid degradation.
• 75A durometer: The medium-hardness shore rating resists penetration and extrusion while still conforming to mating surfaces for effective sealing.
• Round cross-section: The standard round profile creates a reliable seal between overlapping cylindrical surfaces such as pipes, fittings, and bottle caps.
• Pack quantity: Available as a pack of 25, the set provides spares for maintenance shops or multiple repair jobs without frequent reordering.

Who It's For

This product is aimed at mechanics, plumbers working with compatible fluids, firearms and suppressor owners looking for durable replacement seals, and industrial users who need fuel- and heat-resistant o-rings. Those who replace o-rings frequently will appreciate the 25-piece pack and the common size that fits MSA fuel bottles and similar fittings.

It is not ideal for systems exposed to low molecular organic acids, ammonia gas, strong alkalis, amines, glycol-based brake fluids, or super-heated steam, so users working primarily with those media should choose a different elastomer designed for that chemical exposure.

Pros & Cons

Pros

• Excellent chemical and fuel resistance for a wide range of applications and solvents.
• High usable temperature range keeps seals functional from sub-freezing to very hot environments.
• Good durability and value when bought as a pack of 25 for repair and maintenance work.

Cons

• Not compatible with certain acids, amines, alkalis, and glycol-based brake fluids, limiting use in some specialty systems.

Specifications

Our Verdict

The 342 Viton O-ring is a practical choice for users who need dependable fuel and heat resistance with a medium-hard 75A durometer. As a pack of 25, it represents good value for maintenance shops and hobbyists replacing seals on bottles, pumps, and suppressors, provided the service fluids are compatible with Viton.

Frequently Asked Questions

Can these o-rings handle fuel exposure?
Yes, Viton is compatible with many fuels and aromatic/aliphatic hydrocarbons, making these rings suitable for fuel-related seals.

Will they withstand high temperatures?
They are rated to 400 degrees F and work well in high-heat applications within that limit.

Are these o-rings compatible with brake fluid?
No, Viton is vulnerable to glycol-based brake fluids, so avoid use where that fluid is present.