An O-ring is a torus-shaped elastomer or encapsulated seal that seats in a machined gland and is compressed between two mating surfaces to block the passage of liquid or gas. FITCO supplies O-rings across all specialty material families, from certified pharma-grade silicone through to FFKM and FEP/PFA-encapsulated constructions for the most demanding chemical environments.
A specialist choice when standard FKM is unsuitable for steam, amine or alkaline service.
View FEPM →Silicone-like low-temperature flexibility with improved hydrocarbon and fuel resistance.
View FVMQ →Platinum-cured, FDA and USP Class VI compliant sealing for regulated environments.
View Pharma Silicone →Fluoroelastomer chemical resistance with documented food and pharma compliance.
View FDA/USP FKM →A seamless FEP or PFA jacket over an elastomer core for near-universal chemical resistance.
View FEP/PFA Encapsulated →Inch-based standard, 369 standard sizes across dash numbers -001 to -906. The default reference standard in North America and widely cross-referenced globally.
Metric standard defining O-ring dimensions in Series A (inch-derived) and Series B (metric-derived) size series, used extensively in European and Asian OEM equipment.
British Standard metric O-ring sizing, common in UK and Commonwealth-spec industrial and process equipment.
Japanese Industrial Standard sizing, used in Japanese-built machinery, hydraulics and automotive equipment.
Non-standard ID, cross-section or profile manufactured to customer drawing \u2014 common in legacy equipment, retrofit, and OEM-specific designs.
Ring permanently thins and loses contact force \u2014 the most common long-term failure mode, accelerated by heat and time under load.
Wrong material for the process fluid causes softening, swelling or embrittlement \u2014 always the first check when a seal fails early.
Excessive clearance gap combined with high pressure pushes the material into the gap, especially at temperature when the material softens.
Rapid pressure drop causes absorbed gas trapped in the elastomer to expand violently, blistering or rupturing the seal.
Share your size, drawing or existing part number and FITCO will confirm suitable material and availability.
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