Mr O-Ring 256 Viton O-Ring 5-3/4in ID 6in OD Pack of 25 - High Temp

In this review the Mr O-Ring 256 Viton O-Ring pack is evaluated for technicians and hobbyists who need reliable, chemical-resistant seals in demanding environments. The bottom line: this pack of 25 black 90A durometer Viton o-rings is best for applications that require high temperature tolerance and resistance to fuels, oils and many solvents. The reviewer found the consistent dimensions and the wide temperature range to be the single biggest reason to choose these o-rings for preventive maintenance and replacement stores.

Key Features

• Material: FKM Viton construction provides excellent resistance to fuels, mineral oils and many organic solvents, making these o-rings suitable for harsh chemical exposure.
• Durometer: The 90A hardness gives a firm seal that resists extrusion while still compressing enough to maintain a leak-free joint in many static and dynamic uses.
• Temperature range: Rated from -26C to 232C, these o-rings remain usable across very low to very high temperatures encountered in engines and industrial equipment.
• Pack quantity: Supplied as a pack of 25, which is convenient for bulk maintenance, stockrooms or projects requiring multiple identical seals.
• Size accuracy: Nominal and actual dimensions are provided so installers can verify fit; the near-metric equivalents help global users confirm compatibility.
• Shelf life: An effectively unlimited shelf life reduces waste and lets shops buy in quantity without concern for expiry.

Who It's For

These o-rings are aimed at mechanics, maintenance technicians and fabricators who need a dependable seal that resists petroleum, biodiesel blends, silicone oils, and many chemicals. The pack size and standardized sizing make them practical for facilities that perform regular seal replacement or keep spares on hand.

They are less suited for applications that require very soft, low-durometer sealing surfaces or where a non-fluorocarbon elastomer is specified for regulatory reasons. For delicate low-pressure seals that need extreme elasticity, a softer material would be preferable.

Pros & Cons

Pros

• High chemical and heat resistance from the Viton (FKM) compound for demanding environments.
• Consistent 90A hardness balances extrusion resistance with reliable sealing under compression.
• Pack of 25 and clear nominal/actual dimensions make inventory and selection straightforward.

Cons

• Higher durometer may be firmer than desired for some low-pressure or sensitive sealing applications.

Specifications

Material	256 Viton (FKM)
Durometer	90A
Nominal dimensions	5-3/4in ID x 6in OD x 1/8in CS
Actual dimensions	5.734in ID x 6.012in OD x 0.139in CS
Metric dimensions	145.64 mm ID x 152.70 mm OD x 3.53 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	25 o-rings

Our Verdict

The Mr O-Ring 256 Viton pack is a practical, cost-effective choice for anyone needing durable, high-temperature o-rings that resist fuels and many chemicals. Buy it if you need standardized AS568-compatible sizes in quantity for maintenance or projects; avoid it only if you require a much softer elastomer for delicate seals.

Frequently Asked Questions

Are these o-rings compatible with gasoline and diesel?
Yes, Viton (FKM) is suitable for many petroleum products including gasoline, diesel and common fuel blends.

Will the 90A hardness work for dynamic seals?
90A offers good extrusion resistance and can work in many dynamic seals, but specific pump or shaft tolerances should be checked for compatibility.

Do these o-rings expire in storage?
No, the product notes an effectively unlimited shelf life when stored properly away from extreme ozone and sunlight.