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Substantially all O-ring manufacturers present their catalog data in the rotation of “groupings” or “families” of cross-sectional thickness first, then followed by dimensions of inside diameter. All sizes with 1/16” nominal wall are listed first, followed by rings with 3/32” wall, then 1/8” wall, etc.

This is the same mode of presentation found in the ARP 568 Uniform-Numbering System, published as the Aeronautical Recommended Practice Report of the Society of Automotive Engineers. The same practice of detailing sizes by cross-sectional “families” is found in government specifications AN 6227, AN 6230, MS 9021, MS 15993, MS 28775, MS 29513, etc.

O-Ring Design Guide (start Here)

Pressure Seals, Inc.

US Standard Sizes Size Guide
Aerospace O-Ring Standard AS568A
AS568A (Rev 7/1/74) standardized on one class of O-ring tolerances compared with two
on previous issues. The sizes are grouped by cross section and listed numerically. Actual
sizes for inside diameter are referenced by minimum, mean and maximum dimensions.

000 Series / 100 Series / 5/32 Cross Section / 200 Series / 300 Series / 400 Series / 900 Series

Micro Miniatures (+Close Tolerance O-Rings and Seals)

Non-Standard O-Rings by Cross Section

PTFE Coatings

Metric O-Rings (please Call)