O-ring American Standard Specifications (AS-568 Series)
[2026-04-06] | By Xiamen Jinshun Sealing Technology Co., Ltd. Annie Xu
Introduction
If you're sourcing O-rings for international projects-especially in the U.S. market-you'll run into the AS568 standard sooner or later.
This standard defines the most widely used O-ring sizes globally. For OEM buyers, engineers, and procurement teams, understanding AS568 isn't just helpful-it's essential for ensuring compatibility, reducing redesign costs, and speeding up production.
In this guide, we'll break down the AS568 O-ring size system, key dimensions, tolerances, and how to choose the right specification when working with a professional O-ring manufacturer.
What Is the AS568 O-Ring Standard?
The AS568 standard (also known as the SAE Aerospace Standard) is a U.S. sizing system that defines:
- Inner Diameter (ID)
- Cross Section (CS)
- Standard size numbers (e.g., -001 to -475)
- Each "dash number" corresponds to a fixed combination of ID and cross-section.
👉 In simple terms:
Instead of measuring every time, you just specify a dash number, and manufacturers know exactly what size you need.
Why AS568 Matters for OEM Buyers
Using standardized O-rings brings clear advantages:
✅ Global compatibility (especially U.S. and international markets)
✅ Faster sourcing and replacement
✅ Reduced tooling costs
✅ Consistent sealing performance
📊 In industrial procurement, over 70% of standard sealing applications use AS568 sizes due to availability and cost efficiency.
AS568 O-Ring Size Structure Explained
Each AS568 O-ring is defined by:
| Parameter | Description |
|---|---|
| ID (Inner Diameter) | The internal diameter of the O-ring |
| CS (Cross Section) | Thickness of the ring |
| Dash Number | Standard size code (e.g., -214, -325) |
Example
AS568-214
- ID: 0.737 inch (18.72 mm)
- CS: 0.139 inch (3.53 mm)
AS568 O-Ring Size Chart
Standard Cross-Section Series
| Series | Cross Section (inch) | Cross Section (mm) | Typical Use |
|---|---|---|---|
| -0XX | 0.040" | 1.02 mm | Miniature seals |
| -1XX | 0.070" | 1.78 mm | Light-duty applications |
| -2XX | 0.103" | 2.62 mm | General industrial |
| -3XX | 0.139" | 3.53 mm | Hydraulic systems |
| -4XX | 0.210" | 5.33 mm | Heavy-duty sealing |
💡 The -2XX and -3XX series are the most commonly used in industrial and automotive applications.
Tolerance and Precision Requirements
AS568 also defines tolerance levels to ensure proper sealing.
Typical Tolerance Reference
| Parameter | Tolerance Range |
|---|---|
| ID | ±0.08 mm to ±0.25 mm |
| Cross Section | ±0.05 mm to ±0.13 mm |
👉 Why this matters:
Even a 0.1 mm deviation can cause leakage or premature failure in high-pressure systems.
Material Selection for AS568 O-Rings
Size alone isn't enough-the material determines performance.
Common Material Options
| Material | Temperature Range | Key Benefits | Applications |
|---|---|---|---|
| NBR | -40°C to +120°C | Oil resistance | Automotive, hydraulic |
| EPDM | -50°C to +150°C | Water & steam resistance | Drinking water systems |
| Silicone | -60°C to +200°C | Food-grade, flexible | Medical, food equipment |
| FKM (Viton) | -20°C to +250°C | Chemical resistance | Fuel systems |
📌 For drinking water and RO systems, certified EPDM or silicone is required (NSF, WRAS, etc.).
AS568 vs Other O-Ring Standards
| Standard | Region | characteristic |
|---|---|---|
| AS568 | USA / Global | Most widely used |
| ISO 3601 | International | Metric-based |
| JIS B2401 | Japan | Smaller size range |
| GB/T 3452 | China | Local standard |
👉 If your product targets global markets, AS568 is usually the safest choice.
How to Choose the Right AS568 O-Ring
When working with a custom O-ring manufacturer, follow this checklist:
- Confirm dash number (AS568 size)
- Define working conditions (temperature, pressure, media)
- Select material compatibility
- Check certification requirements (FDA, NSF, WRAS, etc.)
- Verify tolerance and surface finish
💡 Early supplier involvement can reduce sealing failures by up to 40% in OEM projects.
Why Choose Jinshun as Your O-Ring Manufacturer
With over 20+ years of experience, Xiamen Jinshun Sealing Technology Co., Ltd. delivers reliable sealing solutions for global buyers.
Our Advantages
- Full AS568 standard production capability
- ISO9001 & ISO14001 certified factory
- Materials compliant with ROHS, REACH, PAHS
- Certified products: NSF, FDA, WRAS, ACS, UL
- Strong OEM/ODM customization support
- Fast sample lead time: 7–15 days
We support industries including:
- Automotive
- Water treatment & RO systems
- Electronics and appliances
- Industrial machinery
FAQs
1. What does AS568 mean in O-rings?
It's a U.S. standard that defines O-ring sizes using dash numbers for easy identification and replacement.
2. Are AS568 O-rings interchangeable globally?
Yes, they are widely used worldwide and considered a global standard for inch-based systems.
3. Can I customize AS568 O-rings?
Absolutely. A professional O-ring manufacturer can adjust material, hardness, and color while keeping standard dimensions.
4. Which AS568 series is most commonly used?
The -2XX and -3XX series are the most widely used in industrial and hydraulic applications.
5. How do I avoid selecting the wrong size?
Always verify:
- Groove dimensions
- Compression rate (15–30%)
- Application pressure
Looking for a trusted O-ring manufacturer who understands AS568 standards and OEM requirements?
Xiamen Jinshun Sealing Technology Co., Ltd. offers:
- Full AS568 size range
- Custom materials and certifications
- Competitive factory pricing
- Fast global delivery
👉 Contact us today for a free quote or technical consultation.
Let's help you choose the right O-ring-accurately, efficiently, and cost-effectively.