238 Viton O-Ring 75A, 3-1/2 in ID 3-3/4 in OD (Pack of 25)

In this review the focus is on the 238 Viton O-ring pack and why it suits technicians, hobbyists, and maintenance teams needing reliable seals for fuel, chemical and high-temperature applications. The bottom line: these black Viton rings deliver durable sealing performance across a wide temperature range and resist many fuels and solvents, making them a practical replacement part for cylinders and bottle seals where heat and chemical exposure are concerns. The pack of 25 also makes it easy to keep spares on hand for routine maintenance or field repairs.

Key Features

• Material: Made from Viton fluorocarbon elastomer, the O-ring offers strong resistance to heat, fuels and many chemicals commonly found in industrial settings.
• Temperature range: Rated to perform from -15 degrees F to 400 degrees F, the ring maintains sealing ability in both cold starts and hot operating conditions.
• Hardness: The 75A shore durometer provides a good balance of flexibility and resistance to penetration for reliable static seals.
• Cross-section: The round cross-section creates a dependable seal between cylindrical overlapping surfaces such as bottle collars and barrel fittings.
• Compatibility: Suitable for non-flammable hydraulic fuels, silicone oil, chlorinated and aromatic hydrocarbons, as well as vacuum and outdoor exposure scenarios.

Who It's For

These O-rings are best for maintenance technicians, plumbing and hydraulic specialists, firearms and suppressor owners, and anyone who needs replacement seals for fuel bottles or cylindrical joints that face heat or fuel exposure. The pack quantity and standard sizing make them convenient for shops that perform frequent replacements.

Those who should look elsewhere include users who require compatibility with strong alkalis, ammonia gas, amines, glycol-based brake fluids, or super-heated steam, since Viton is vulnerable to those substances. If an application demands extreme flexibility below -26 degrees C or immersion in aggressive acids, a different elastomer may be a better choice.

Pros & Cons

Pros

• Excellent heat and fuel resistance that holds up under high temperatures and hot components.
• Pack of 25 offers clear value for frequent replacements and maintenance spares.
• Customers report accurate fit and reliable leak resistance in common uses such as fuel bottles and barrel seals.

Cons

• Not suitable for exposure to low molecular organic acids, ammonia, alkalis or glycol-based brake fluids.
• The 75A hardness may feel too firm for some dynamic sealing applications that need softer seals.

Specifications

Our Verdict

The 238 Viton O-ring pack is a dependable, cost-effective option for anyone needing robust static seals exposed to heat, fuels, or common hydrocarbons. With a practical size, 75A hardness and a broad temperature range, it is a smart buy for maintenance shops and users replacing bottle and barrel seals, provided the application does not involve known Viton incompatibilities.

Frequently Asked Questions

Can these O-rings be used with gasoline and aromatic fuels?
Yes; Viton is compatible with many fuels and aromatic hydrocarbons, making these rings suitable for fuel-facing seals.

Are they suitable for high vacuum systems?
Yes; Viton can be used in high vacuum environments, though installation and cleanliness affect performance.

Will these resist ozone and weathering outdoors?
Yes; Viton has good ozone and weathering resistance for outdoor exposure within the specified temperature range.