337 Viton O-Ring 3in ID 75A - Durable Chemical and Fuel Seal

In this review of the 337 Viton O-ring, the bottom line is simple: this pack of ten is for anyone needing a small, reliable seal that resists heat, fuels, and many chemicals. The reviewer found the round, black Viton compound and 75A durometer deliver a firm, durable seal useful in fuel bottles, plumbing fixtures, and firearm or suppressor switchback applications. Its operating range from -15 degrees F to 400 degrees F and compatibility with aromatic and aliphatic hydrocarbons are the single biggest reasons a technician or hobbyist would choose these O-rings over general-purpose elastomers.

Key Features

• Material: Made of Viton fluorocarbon elastomer for superior resistance to fuels, many chemicals, ozone, and weathering.
• Temperature range: Can be used between -15 degrees F and 400 degrees F, giving broad utility across hot engine and cold storage applications.
• Durometer: 75A hardness provides good resistance to penetration while still compressing to form a reliable seal between cylindrical surfaces.
• Form factor: Round cross-section and precise 3in ID with 3-3/8in OD produce consistent sealing where overlapping cylindrical parts meet.
• Standards: Conforms to the AS568A sizing standard, making it easier to match and replace existing O-rings in common inventories.
• Pack quantity: Supplied as a pack of 10 so multiple spares are available for maintenance or repeated replacements.

Who It's For

This O-ring is suited for maintenance technicians, hobbyists, and industrial users who need a chemical- and fuel-resistant seal in compact cylindrical assemblies. It is particularly useful for applications such as fuel bottle seals, certain firearm barrel or suppressor seals, and low to medium pressure hydraulic or pneumatic fittings where Viton compatibility is required.

Those who should look elsewhere include users who need compatibility with strong alkalis, ammonia, glycol-based brake fluids, or super-heated steam, since Viton is vulnerable to those media. Also consider a softer or harder durometer if a different compression characteristic is essential for your assembly.

Pros & Cons

Pros

• Excellent chemical and fuel resistance for long-lasting performance in contact with hydrocarbons and many solvents.
• Wide usable temperature window from -15 degrees F to 400 degrees F for versatile deployment.
• 75A durometer balances durability and sealability, and customers report good fit and leak resistance in real-world replacements.
• Pack of 10 offers value and convenient spares for recurring maintenance.

Cons

• Not compatible with low molecular organic acids, ammonia, certain alkalis, and glycol-based brake fluids, so it is not universal for all chemical exposures.
• 75A hardness may be firmer than desired for some delicate sealing surfaces that require a softer material.

Specifications

Our Verdict

The 337 Viton O-ring is a practical, cost-effective choice for anyone needing a durable, fuel- and chemical-resistant seal in cylindrical assemblies. It is good value as a pack of 10 for routine maintenance and replacement when compatibility with hydrocarbons and high temperatures matters, but users exposed to alkalis or glycol brake fluids should select a different compound.

Frequently Asked Questions

Are these O-rings suitable for fuel contact?
Yes, Viton is compatible with many fuels and aromatic and aliphatic hydrocarbons, making these O-rings appropriate for fuel-contact seals.

What temperature range do they handle?
They are rated for use from -15 degrees F up to 400 degrees F, suitable for most engine and heated applications.

Will these work with brake fluid or ammonia?
No, Viton is vulnerable to glycol-based brake fluids and ammonia, so these compounds should be avoided for those media.