AS568-231 FS70 Fluorosilicone (FVMQ) 70 Duro O-Ring

Dimensions: 2-5/8" ID x 2-7/8" OD x 1/8" CS

The AS568-231 is a Fluorosilicone (FVMQ) 70A durometer O-Ring with an inside diameter of 2.609 inches and a cross-section of 0.139 inches. It is built for fuel systems and wide temperature swings, the spot where plain silicone gives up on fuel and standard rubber gives up on heat and cold. This O-Ring is stocked and shipped same-day by The O-Ring Store LLC, an ISO 9001:2015 certified distributor.

Stop fuel leaks and seal parts that see both heat and cold with the AS568-231 Fluorosilicone (FVMQ) O-Ring. This 70A durometer seal handles jet fuel and diester-based lubricants while staying flexible from -76F all the way to +392F. That makes it a solid pick for the jobs below, and a reliable replacement when a lesser O-Ring swells, cracks or takes a set.

Operating Temperature: -76 to +392F (-60 to +200C)

Material and Performance Details

Fluorosilicone O-Rings are a silicone and FKM hybrid seal, used for fuel and lubricant resistance across a wide temperature range. This FVMQ 70 durometer compound handles jet fuel, diester-based lubricants and oxygen plasma up to 392F, which makes it a solid pick for aerospace, automotive and semiconductor ashing equipment. These blue O-Rings meet MIL-DTL-25988/1 and AMS-R-25988 Class 1 Grade 70, so you can match the exact spec you need. Fluorosilicone also holds up well to aging and sunlight and stays flexible in the cold. The 70A durometer gives good squeeze and a firm seal without going brittle.

• Excellent resistance to: jet fuel, aviation fuels, gasoline, diesel, diester-based lubricants, engine and machine oils, oxygen plasma, ozone, UV, sunlight and weathering
• Limited capability with: high-pressure steam, hot water, phosphate esters
• Not compatible with: ketones such as MEK, strong acids, automotive and aircraft brake fluids, amines

Sizes and Measurements

• Dimensions: 2-5/8" ID x 2-7/8" OD x 1/8" CS
• Actual: 2.609" ID x 2.887" OD x 0.139" CS
• Metric: 66.27mm ID x 73.33mm OD x 3.53mm CS
• Part Number: FS70231
• AS568 Dash Number: -231
• Cross-references: Parker 2-231 (3.53mm CS / 0.139" CS)

Applications and Use Cases

Fluorosilicone O-Rings earn their keep in aerospace and defense fuel systems. You will find them in aircraft fuel lines, pumps, injectors, filters and fittings, where the part has to shrug off jet fuel and still flex after a cold soak at altitude. They also show up in automotive fuel systems and semiconductor ashing equipment, where oxygen plasma resistance matters. When plain silicone would swell in fuel and standard nitrile would crack in the cold, FVMQ keeps sealing.

• Aircraft fuel lines and fittings
• Fuel pumps and injectors
• Fuel filters and manifolds
• Aerospace and defense fuel systems
• Automotive fuel systems
• Semiconductor ashing equipment (oxygen plasma exposure)
• Cold-soak service at altitude

Key Specifications

• Material: Fluorosilicone (FVMQ)
• Durometer: 70A Shore A
• Color: Blue
• Standard: MIL-DTL-25988/1 and AMS-R-25988 Class 1 Grade 70
• Temperature Range: -76 to +392F (-60 to +200C)

Why Buy from The O-Ring Store LLC

The O-Ring Store LLC is an ISO 9001:2015 certified distributor with USA stock for fast delivery. Most in-stock items ship the same day. We handle custom sizes, and we can send full lot traceability and documentation when you need it. Every order gets checked through our Olypsys® scan-based quality system before it leaves the building. Fair pricing, real people and no runaround. We make getting O-Rings easy!

Frequently Asked Questions

Q: What are the exact dimensions of the AS568-231 O-Ring?
A: The AS568-231 O-Ring has an actual inside diameter of 2.609 inches (66.27mm), a cross-section of 0.139 inches (3.53mm) and an outside diameter of 2.887 inches (73.33mm).

Q: Is Fluorosilicone good for fuel?
A: Yes. FVMQ resists jet fuel, gasoline, diesel and diester-based lubricants, which is why it is common in aircraft and automotive fuel systems.

Q: What is the Parker equivalent of the AS568-231 O-Ring?
A: The Parker cross-reference for the AS568-231 is the Parker 2-231. Both share the same 0.139-inch (3.53mm) cross-section and 2.609-inch (66.27mm) inside diameter per the AS568 standard.