AS568 O-Ring Standard: Quick Reference Size & Material Guide
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The AS568 specification (Aerospace Standard 568) is the most widely recognized standard for imperial O-ring sizing across North America and global engineering sectors. Each size is designated by a standardized 3-digit dash number, eliminating confusion when specifying inner diameter (ID) and cross-section (CS).
This quick-reference guide outlines the 5 primary AS568 cross-section series, common dash sizes with metric conversions, and material selection criteria to help you find or order the exact O-rings for your assembly.
The 5 Primary AS568 Cross-Section Series
AS568 organizes O-rings into five main cross-section categories according to the first digit of the dash number:
- 000 Series (CS 0.070 in / 1.78 mm): Compact cross-section designed for miniature valves, precision instrumentation, and compact enclosures.
- 100 Series (CS 0.103 in / 2.62 mm): Versatile general-purpose size used across automotive connectors, fluid lines, and electrical housings.
- 200 Series (CS 0.139 in / 3.53 mm): Sturdy cross-section commonly used in hydraulic manifolds, pneumatic cylinders, and piping flanges.
- 300 Series (CS 0.210 in / 5.33 mm): Heavy-duty profile engineered for high-pressure fluid power, heavy machinery, and larger cylinder caps.
- 400 Series (CS 0.275 in / 6.99 mm): Extra-thick profile for large pressure vessels, pipeline flanges, and heavy static seals.
Common AS568 Dash Sizes Quick Reference
Below is a quick reference of frequently specified AS568 dash sizes with both imperial and metric dimensions:
| Dash # | Inside Diameter (Inches) | Inside Diameter (mm) | Cross Section (Inches) | Cross Section (mm) |
|---|---|---|---|---|
| -010 | 0.239 in | 6.07 mm | 0.070 in | 1.78 mm |
| -014 | 0.489 in | 12.42 mm | 0.070 in | 1.78 mm |
| -110 | 0.362 in | 9.19 mm | 0.103 in | 2.62 mm |
| -114 | 0.612 in | 15.54 mm | 0.103 in | 2.62 mm |
| -210 | 0.734 in | 18.64 mm | 0.139 in | 3.53 mm |
| -214 | 0.984 in | 24.99 mm | 0.139 in | 3.53 mm |
| -325 | 1.475 in | 37.47 mm | 0.210 in | 5.33 mm |
Elastomer Materials and Operating Parameters
Matching the dash size with the correct polymer ensures leak-free reliability under operating pressure and temperature:
- NBR (Nitrile) 70 / 90 Shore A: Temperature resistance from -30°C to +100°C (-22°F to +212°F). Excellent resistance to petroleum-based oils, fuels, and hydraulic oils.
- FKM (Fluoroelastomer) 75 Shore A: Temperature resistance from -20°C to +200°C (-4°F to +392°F). High resistance to synthetic fluids, aggressive chemicals, and elevated thermal environments.
- Silicone (VMQ) 60 / 70 Shore A: Wide operating range from -60°C to +250°C (-76°F to +482°F). Excellent elasticity, compression set resistance, and environmental sealing.
- EPDM 70 Shore A: Temperature range from -40°C to +120°C (-40°F to +248°F). High resistance to weathering, ozone, hot water, and steam.
Need AS568 Standard or Non-Standard O-Rings?
We stock many popular AS568 dash sizes in NBR, FKM, Silicone, and EPDM. Whether you need standard sizes or custom dimensional tolerances with low MOQ, please send us your inquiry through our Contact Page to receive a direct quote within 24 hours.