AS568-121 O-Ring

Inside diameter 1.049″
Cross-section 0.103″
Outside diameter 1.255″
Metric (ID × CS) 26.64 × 2.62 mm

OD is derived: ID + 2 × CS = 1.049″ + 2 × 0.103″ = 1.255″.

Neighboring sizes (CS 0.103″ series)

Dash ID OD ID mm vs -121
-119 0.924″ 1.130″ 23.47 ID −0.125″
-120 0.987″ 1.193″ 25.07 ID −0.062″
-121 1.049″ 1.255″ 26.64
-122 1.112″ 1.318″ 28.24 ID +0.063″
-123 1.174″ 1.380″ 29.82 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.