Mr O-Ring 240 Viton O-Ring 3-3/4 in ID 4 in OD - Pack of 25

In this review the focus is on a workhorse sealing part: the 240 Viton O-Ring in a pack of 25. The bottom line is simple - this kit is aimed at technicians, mechanics and maintenance crews who need reliable, high-temperature resistant seals in common AS568 sizes. The reviewer found the material and dimensions match typical industrial expectations, and the long temperature range and chemical compatibility make these o-rings a straightforward choice when replacing seals exposed to fuels, oils or high heat.

Key Features

• Material: Made from Viton (FKM), these o-rings resist high temperatures and a wide range of chemicals, which keeps seals intact under demanding service conditions.
• Durometer: The 90A hardness provides a durable, firm seal that holds shape under compression and performs well in static and some dynamic applications.
• Pack size: Supplied as a pack of 25, the quantity is useful for routine maintenance and stocking common replacement parts on the shop shelf.
• Temperature range: Rated from -26C (-15F) to 232C (450F), the rings cover both low-temperature starts and sustained high-heat operation without rapid degradation.
• Dimensional accuracy: Nominal and measured dimensions are close (3-3/4 in ID nominal; actual 3.734 in ID and 4.012 in OD), which helps when matching to AS568 size standards.
• Chemical compatibility: Performs well with petroleum products, fuels, biodiesel blends, mineral and silicone oils, and resists ozone and weathering for outdoor or exposed use.

Who It's For

This product is best for industrial maintenance, plumbing and hydraulic technicians who need a reliable, heat-resistant o-ring in a common AS568 size. The pack of 25 makes it practical for on-site repairs, scheduled maintenance, and stocking in a parts cabinet for repeat service needs.

Those who need extreme low-temperature flexibility, very soft sealing material for delicate dynamic shafts, or custom compound formulations for specialty chemicals should look elsewhere. For general-purpose high-temp and fuel-exposed sealing, these Viton o-rings are a sensible choice.

Pros & Cons

Pros

• High temperature and chemical resistance from the Viton (FKM) compound gives long service life in fuel and oil environments.
• 90A durometer provides a robust seal that maintains shape and compression for many static applications.
• Pack of 25 is convenient for maintenance teams and reduces the need for frequent reordering.

Cons

• Higher durometer means the rings are firmer; they may not be ideal for very low-pressure or delicate dynamic sealing where a softer material is preferred.

Specifications

Our Verdict

The Mr O-Ring 240 Viton pack of 25 is a practical, value-oriented choice for technicians who need dependable, high-temperature and fuel-resistant seals in a common AS568 size. It is especially good for static sealing and routine maintenance stocking; those needing softer compounds for delicate dynamic seals should consider alternative materials.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes. The Viton compound is compatible with petroleum fuels, diesel and common fuel blends including biodiesel and methanol/ethanol blends.

Do the dimensions match AS568 sizing?
Yes. The product is offered to meet AS568 size standards and the actual measurements closely match the nominal 3-3/4 in ID specification.

Can these be used for high-temperature applications?
Yes. The rings are rated to 232C (450F), making them suitable for many high-heat sealing situations.