What do O-ring ID and CS mean?

ID is the inside diameter of the relaxed ring and CS is the cross-section (the thickness of the rubber cord). An O-ring is fully specified by its ID and CS, e.g. 9.8 mm ID with 1.9 mm CS.

What is the difference between JIS B 2401 P, G and S series?

In JIS B 2401, P-series rings are intended for both motion and fixed (static) use, G-series for fixed/static use, and S-series are small-diameter rings with a thin 1.5 mm cross-section. Each series pairs nominal numbers with defined ID and CS values.

How are AS568 dash numbers organized?

AS568 groups rings by cross-section: the 0-series is 1.78 mm (0.070 in), the 100-series 2.62 mm (0.103 in), the 200-series 3.53 mm (0.139 in), the 300-series 5.33 mm (0.210 in) and the 400-series 6.99 mm (0.275 in). The dash number then sets the inside diameter within that cross-section.

Can I substitute a JIS P-series ring for an AS568 ring?

Not directly. The two systems use different cross-sections and inside diameters, so dimensions rarely match exactly. Always compare both ID and CS and verify against the groove design rather than assuming equivalence.

Are these all available O-ring sizes?

No. This chart lists representative, commonly used sizes only. Each standard defines many more sizes. Confirm exact dimensions, tolerances and groove design against the standard or the manufacturer before ordering.

Reference

O-Ring Size Chart

Representative JIS B 2401 (P / G / S) and AS568 O-ring sizes. Look up inside diameter (ID) and cross-section (CS) by nominal number, or type an ID in mm to find the nearest standard size.