AS568-331 O-Ring

Inside diameter 2.225″
Cross-section 0.210″
Outside diameter 2.645″
Metric (ID × CS) 56.52 × 5.33 mm

OD is derived: ID + 2 × CS = 2.225″ + 2 × 0.210″ = 2.645″.

Neighboring sizes (CS 0.210″ series)

Dash ID OD ID mm vs -331
-329 1.975″ 2.395″ 50.16 ID −0.250″
-330 2.100″ 2.520″ 53.34 ID −0.125″
-331 2.225″ 2.645″ 56.52
-332 2.350″ 2.770″ 59.69 ID +0.125″
-333 2.475″ 2.895″ 62.87 ID +0.250″
Data provenance. SAE AS568, Aerospace Size Standard for O-rings (SAE International). Nominal dimensions per AS568; size tolerances vary by dash number and are not yet cataloged. Groove/gland design depends on the application — consult a gland design reference. See all data sources.