AS568 O-Ring Size Guide
The inch-based dash-number system: how AS568 series and cross-sections work, with common sizes converted to millimetres.
AS568 assigns every O-ring a three-digit dash number. The first digit selects the cross-section series — 0xx ≈ 1.78 mm (0.070″), 1xx ≈ 2.62 mm (0.103″), 2xx ≈ 3.53 mm (0.139″), 3xx ≈ 5.33 mm (0.210″), 4xx ≈ 6.99 mm (0.275″) — and the remaining digits step through inside diameters in regular inch increments.
The table below lists a curated subset of frequently used dash sizes converted to millimetres. Inside-diameter tolerances shown are typical band values; confirm exact tolerances in the current standard revision before release drawings.
Common AS568 sizes (metric)
| Designation | Nominal ID mm | Cross-section mm | Nominal OD mm | ID tol. ±mm | CS tol. ±mm |
|---|---|---|---|---|---|
| -006 | 2.90 | 1.78 | 6.46 | 0.13 | 0.08 |
| -008 | 4.47 | 1.78 | 8.03 | 0.13 | 0.08 |
| -010 | 6.07 | 1.78 | 9.63 | 0.13 | 0.08 |
| -012 | 9.25 | 1.78 | 12.81 | 0.13 | 0.08 |
| -014 | 12.42 | 1.78 | 15.98 | 0.20 | 0.08 |
| -016 | 15.60 | 1.78 | 19.16 | 0.20 | 0.08 |
| -018 | 18.77 | 1.78 | 22.33 | 0.20 | 0.08 |
| -020 | 21.95 | 1.78 | 25.51 | 0.20 | 0.08 |
| -022 | 25.12 | 1.78 | 28.68 | 0.30 | 0.08 |
| -024 | 28.30 | 1.78 | 31.86 | 0.30 | 0.08 |
| -026 | 31.47 | 1.78 | 35.03 | 0.30 | 0.08 |
| -028 | 34.65 | 1.78 | 38.21 | 0.30 | 0.08 |
| -110 | 9.19 | 2.62 | 14.43 | 0.13 | 0.08 |
| -112 | 12.37 | 2.62 | 17.61 | 0.20 | 0.08 |
| -114 | 15.54 | 2.62 | 20.78 | 0.20 | 0.08 |
| -116 | 18.72 | 2.62 | 23.96 | 0.20 | 0.08 |
| -118 | 21.89 | 2.62 | 27.13 | 0.20 | 0.08 |
| -120 | 25.07 | 2.62 | 30.31 | 0.30 | 0.08 |
| -122 | 28.24 | 2.62 | 33.48 | 0.30 | 0.08 |
| -124 | 31.42 | 2.62 | 36.66 | 0.30 | 0.08 |
| -126 | 34.59 | 2.62 | 39.83 | 0.30 | 0.08 |
| -128 | 37.77 | 2.62 | 43.01 | 0.30 | 0.08 |
| -132 | 44.12 | 2.62 | 49.36 | 0.30 | 0.08 |
| -136 | 50.47 | 2.62 | 55.71 | 0.50 | 0.08 |
| -140 | 56.82 | 2.62 | 62.06 | 0.50 | 0.08 |
| -210 | 18.64 | 3.53 | 25.70 | 0.20 | 0.10 |
| -212 | 21.82 | 3.53 | 28.88 | 0.20 | 0.10 |
| -214 | 24.99 | 3.53 | 32.05 | 0.20 | 0.10 |
| -216 | 28.17 | 3.53 | 35.23 | 0.30 | 0.10 |
| -218 | 31.34 | 3.53 | 38.40 | 0.30 | 0.10 |
| -220 | 34.52 | 3.53 | 41.58 | 0.30 | 0.10 |
| -222 | 37.69 | 3.53 | 44.75 | 0.30 | 0.10 |
| -224 | 44.04 | 3.53 | 51.10 | 0.30 | 0.10 |
| -226 | 50.39 | 3.53 | 57.45 | 0.50 | 0.10 |
| -228 | 56.74 | 3.53 | 63.80 | 0.50 | 0.10 |
| -230 | 63.09 | 3.53 | 70.15 | 0.50 | 0.10 |
| -232 | 69.44 | 3.53 | 76.50 | 0.50 | 0.10 |
| -235 | 78.97 | 3.53 | 86.03 | 0.50 | 0.10 |
| -240 | 94.84 | 3.53 | 101.90 | 0.50 | 0.10 |
| -245 | 110.72 | 3.53 | 117.78 | 0.90 | 0.10 |
| -250 | 126.59 | 3.53 | 133.65 | 0.90 | 0.10 |
| -325 | 37.47 | 5.33 | 48.13 | 0.30 | 0.13 |
| -327 | 43.82 | 5.33 | 54.48 | 0.30 | 0.13 |
| -330 | 53.34 | 5.33 | 64.00 | 0.50 | 0.13 |
| -334 | 66.04 | 5.33 | 76.70 | 0.50 | 0.13 |
| -338 | 78.74 | 5.33 | 89.40 | 0.50 | 0.13 |
| -342 | 91.44 | 5.33 | 102.10 | 0.50 | 0.13 |
| -346 | 104.14 | 5.33 | 114.80 | 0.90 | 0.13 |
| -350 | 116.84 | 5.33 | 127.50 | 0.90 | 0.13 |
| -355 | 132.71 | 5.33 | 143.37 | 0.90 | 0.13 |
| -360 | 148.59 | 5.33 | 159.25 | 0.90 | 0.13 |
| -425 | 113.66 | 6.99 | 127.64 | 0.90 | 0.15 |
| -428 | 123.19 | 6.99 | 137.17 | 0.90 | 0.15 |
| -430 | 129.54 | 6.99 | 143.52 | 0.90 | 0.15 |
| -432 | 135.89 | 6.99 | 149.87 | 0.90 | 0.15 |
| -436 | 148.59 | 6.99 | 162.57 | 0.90 | 0.15 |
| -440 | 161.29 | 6.99 | 175.27 | 0.90 | 0.15 |
| -444 | 173.99 | 6.99 | 187.97 | 0.90 | 0.15 |
| -448 | 186.69 | 6.99 | 200.67 | 0.90 | 0.15 |
| -452 | 199.39 | 6.99 | 213.37 | 0.90 | 0.15 |
Source & version
SAE AS568 (Aerospace Size Standard for O-rings)。尺寸取自广泛发布的 AS568 尺寸表，需对照现行修订版核实。 · 现行修订版待核对（常见引用为 AS568D）
Standard size data is for preliminary engineering selection only. Final purchasing and design should be verified against the applicable standard edition, supplier data sheets and actual operating conditions.