AS568-309 O-Ring

Inside diameter 0.412″
Cross-section 0.210″
Outside diameter 0.832″
Metric (ID × CS) 10.46 × 5.33 mm

OD is derived: ID + 2 × CS = 0.412″ + 2 × 0.210″ = 0.832″.

Neighboring sizes (CS 0.210″ series)

Dash ID OD ID mm vs -309
-309 0.412″ 0.832″ 10.46
-310 0.475″ 0.895″ 12.06 ID +0.063″
-311 0.537″ 0.957″ 13.64 ID +0.125″
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.