AS568-205 O-Ring

Inside diameter 0.421″
Cross-section 0.139″
Outside diameter 0.699″
Metric (ID × CS) 10.69 × 3.53 mm

OD is derived: ID + 2 × CS = 0.421″ + 2 × 0.139″ = 0.699″.

Neighboring sizes (CS 0.139″ series)

Dash ID OD ID mm vs -205
-203 0.296″ 0.574″ 7.52 ID −0.125″
-204 0.359″ 0.637″ 9.12 ID −0.062″
-205 0.421″ 0.699″ 10.69
-206 0.484″ 0.762″ 12.29 ID +0.063″
-207 0.546″ 0.824″ 13.87 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.