Side-by-Side Comparison
O-Rings & Rotary Seals
AS568 O-Ring Sizes vs. Metric O-Rings
Comparing 2 standards across 16 specifications. 16 key differences identified.
Comparing:
AS568 O-Ring Sizes
Metric O-Rings
Aerospace Standard AS568 (SAE AS568 / ISO 3601-1) classifies inch-series elastomeric O-rings into five cross-section diameter series: 000 (1/16" / 1.78 mm), 100 (3/32" / 2.62 mm), 200 (1/8" / 3.53 mm), 300 (3/16" / 5.33 mm), and 400 (1/4" / 6.99 mm).
Metric O-rings under ISO 3601-1 and DIN 3771 are designated directly by inside diameter (d_1) and cross-section cord diameter (d_2) in millimeters (e.g. 15.0 × 2.5 mm), matching standard metric groove depths and dynamic cylinder bores.
Specification Comparison Table
16 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standards
|
SAE AS568D / ISO 3601-1 Class A / MIL-STD-120 | ISO 3601-1 (Class A & B tolerances) / DIN 3771-1 |
|
000 Series Cross-Section (1/16")
|
CS: 0.070 in ± 0.003 in (1.78 mm ± 0.08 mm) | Dash -001 to -050 | — |
|
100 Series Cross-Section (3/32")
|
CS: 0.103 in ± 0.003 in (2.62 mm ± 0.08 mm) | Dash -102 to -178 | — |
|
200 Series Cross-Section (1/8")
|
CS: 0.139 in ± 0.004 in (3.53 mm ± 0.10 mm) | Dash -201 to -284 | — |
|
300 Series Cross-Section (3/16")
|
CS: 0.210 in ± 0.005 in (5.33 mm ± 0.13 mm) | Dash -309 to -395 | — |
|
400 Series Cross-Section (1/4")
|
CS: 0.275 in ± 0.006 in (6.99 mm ± 0.15 mm) | Dash -425 to -475 | — |
|
900 Series (Straight Thread Tube Fitting)
|
Boss seals for SAE J1926/MS33649 (Dash -901 to -932) | — |
|
Standard Static Gland Squeeze
|
15% to 30% radial or axial compression | — |
|
Standard Dynamic Gland Squeeze
|
10% to 20% radial compression (reduces friction and seal wear) | — |
|
Common Elastomer Polymers
|
NBR (Buna-N 70/90A), FKM (Viton), EPDM, Silicone (VMQ), FFKM (Kalrez) | — |
|
Callout Designation
|
— | [Inside Diameter d₁ in mm] × [Cross-Section d₂ in mm] (e.g. 20.0 × 3.0) |
|
Standard Metric Cord Sizes (d₂)
|
— | 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 5.7, 6.0, 7.0, 8.0 mm |
|
Micro / Miniature Metric Series
|
— | 0.5 mm to 1.2 mm cross-section for watch crowns and precision instruments |
|
Static Gland Compression Ratio
|
— | 18% to 28% of cord diameter d₂ |
|
Dynamic Gland Compression Ratio
|
— | 10% to 18% of cord diameter d₂ |
|
Hardness Benchmark
|
— | 70 Shore A (General pneumatic/hydraulic) vs 90 Shore A (High pressure > 100 bar) |