345 Viton O-Ring 75A 4in ID 4-3/8in OD - High Temp Chemical Seal

In this review the 345 Viton O-ring is evaluated as a robust sealing solution for demanding fluid and fuel applications; the main reason to buy is its chemical and temperature resilience. The reviewer found these black, round O-rings especially useful where heat, fuel exposure, or aggressive solvents are present, and notes they arrive as a pack of 100 suitable for repeated replacements. For anyone needing a reliable, AS568A-size replacement with a mid-range hardness, this O-ring delivers consistent fit and long service life.

Key Features

• Material: Made of Viton fluorocarbon elastomer to resist a wide range of fuels and chemicals for longer seal life.
• Temperature range: Usable from -15 degrees F to 400 degrees F, allowing installation in both cold starts and high-heat systems.
• Durometer: 75A hardness gives a balance of compression resistance and flexibility for durable sealing under pressure.
• Cross-section: Round profile provides a standard, reliable seal between overlapping cylindrical parts and shafts.
• Standards: Sized to meet Aerospace Standard AS568A which ensures common interchangeability in many fittings.
• Pack quantity: Supplied as a bulk pack of 100, making it economical for maintenance and repeated replacements.

Who It's For

These O-rings are best for technicians, hobbyists, and maintenance teams working with hydraulic or fuel systems, chemical handling equipment, and vacuum or ozone-exposed assemblies. They suit replacement tasks on items like MSA fuel bottles, barrel seals, and similar cylindrical interfaces where AS568A sizing and chemical resistance matter.

Customers who regularly expose seals to low molecular organic acids, ammonia, strong alkalis, or glycol-based brake fluids should look elsewhere; Viton is vulnerable to those media. If a softer elastomer or food-grade approval is required, select a material matched to that specification instead of this 75A Viton.

Pros & Cons

Pros

• Excellent resistance to fuels, aromatic and aliphatic hydrocarbons, and many solvents for reliable performance.
• Wide usable temperature range from -15 degrees F to 400 degrees F for versatile installations.
• Good value supplied in a 100-pack for frequent maintenance or inventory stocking.
• Meets AS568A sizing so it fits common standard grooves and fittings without guesswork.

Cons

• Not compatible with low molecular organic acids, ammonia gas, strong alkalis, amines, and glycol-based brake fluids, so chemical compatibility must be checked.
• 75A hardness may be firmer than desired for some delicate or low-compression applications.

Specifications

Our Verdict

The 345 Viton O-ring is a sensible choice for anyone needing an economical, chemically resistant seal in fuel, solvent, and high-temperature environments; its AS568A sizing and 75A hardness strike a useful balance for many maintenance tasks. Buyers should verify compatibility with specific chemicals like glycol-based fluids or strong alkalis before fitting, but for general fuel and heat exposure this pack of 100 represents solid value and dependable performance.

Frequently Asked Questions

Are these O-rings compatible with fuel?
Yes, Viton is compatible with many fuels including aromatic and aliphatic hydrocarbons and works well in non-flammable hydraulic fuels.

What temperature range will they withstand?
They are rated for use from -15 degrees F up to 400 degrees F, suitable for most heat-exposed seals.

Will they resist brake fluid and ammonia?
No, Viton is vulnerable to glycol-based brake fluids, ammonia gas, and some strong alkalis, so avoid those fluids.