AS568-255 O-Ring

Inside diameter 5.609″
Cross-section 0.139″
Outside diameter 5.887″
Metric (ID × CS) 142.47 × 3.53 mm

OD is derived: ID + 2 × CS = 5.609″ + 2 × 0.139″ = 5.887″.

Neighboring sizes (CS 0.139″ series)

Dash ID OD ID mm vs -255
-253 5.359″ 5.637″ 136.12 ID −0.250″
-254 5.484″ 5.762″ 139.29 ID −0.125″
-255 5.609″ 5.887″ 142.47
-256 5.734″ 6.012″ 145.64 ID +0.125″
-257 5.859″ 6.137″ 148.82 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.