---
type: "o-ring"
dash_number: "155"
designation: "AS568-155"
cs_series: "102-178"
cs_series_name: "AS568 3/32 in series"
id_in: 3.987
id_mm: 101.27
cs_in: 0.103
cs_mm: 2.62
od_in: 4.193
od_mm: 106.51
id_tol_in: 0.028
cs_tol_in: 0.0031
standard: "SAE AS568; MIL-G-5514G (public domain, inactive for new design)"
verified: "August 1, 2026"
url: https://shopmath.org/o-rings/as568-155
---

# AS568-155 O-Ring Size — ID, Cross-Section and OD

An AS568-155 o-ring has an inside diameter of 3.9870 in (101.270 mm) and a 0.1030 in (2.620 mm) cross-section, for an outside diameter of 4.1930 in (106.510 mm). It belongs to the AS568 3/32 in series band.

- **Dash number**: 155
- **Cross-section series**: AS568 3/32 in series
- **Inside diameter**: 3.9870 in (101.270 mm)
- **Cross-section**: 0.1030 in (2.620 mm)
- **Outside diameter**: 4.1930 in (106.510 mm)
- **Standard**: SAE AS568; MIL-G-5514G (public domain, inactive for new design)

## AS568-155 Dimensions and Tolerances

| Dimension | Inch | Millimetre |
| --- | --- | --- |
| Inside diameter (ID) | 3.9870 | 101.270 |
| Cross-section (CS) | 0.1030 | 2.620 |
| Outside diameter (OD) | 4.1930 | 106.510 |
| ID tolerance | ±0.0280 | ±0.710 |
| CS tolerance | ±0.0031 | ±0.080 |

_Outside diameter is computed as ID + 2 × CS; AS568 tabulates ID and CS._

## Gland Design for AS568-155

Static gland dimensions for the 0.103 in cross-section. Depth is the groove depth that produces the stated squeeze on a nominal ring.

| Application | Squeeze | Squeeze (in) | Gland depth (in) | Gland depth (mm) |
| --- | --- | --- | --- | --- |
| Static face seal | 20–30% | 0.0206 – 0.0309 | 0.0721 – 0.0824 | 1.831 – 2.093 |

_Gland depth is computed as CS − (CS × squeeze %), then checked against the published design charts. Groove width, corner radius and back-up ring allowances are outside this dataset._

## O-Ring Sizes Closest to AS568-155

Nearest AS568 sizes by inside diameter — the substitutes to check when this one is out of stock.

| Size | ID (in) | ID (mm) | CS (in) | OD (in) |
| --- | --- | --- | --- | --- |
| [AS568-045](https://shopmath.org/o-rings/as568-045.md) | 3.9890 | 101.320 | 0.0700 | 4.1290 |
| [AS568-242](https://shopmath.org/o-rings/as568-242.md) | 3.9840 | 101.190 | 0.1390 | 4.2620 |
| [AS568-345](https://shopmath.org/o-rings/as568-345.md) | 3.9750 | 100.970 | 0.2100 | 4.3950 |
| [AS568-346](https://shopmath.org/o-rings/as568-346.md) | 4.1000 | 104.140 | 0.2100 | 4.5200 |
| [AS568-243](https://shopmath.org/o-rings/as568-243.md) | 4.1090 | 104.370 | 0.1390 | 4.3870 |
| [AS568-241](https://shopmath.org/o-rings/as568-241.md) | 3.8590 | 98.020 | 0.1390 | 4.1370 |

## Sources and Method for AS568-155

### AS568 dimensions

- **Source**: bd_warehouse o-ring_parameters.csv (Apache-2.0) and bckasper3/KasperCalc oring-sizes.js (MIT), agreeing on all 349 sizes; OD computed as ID + 2 x CS
- **Method**: computed+compiled
- **Verified against**: two independent open datasets agreeing on all 349 sizes; fabricated-dataset negative control passed; 21 checks total

### Gland design

- **Source**: MIL-G-5514G (public domain) gland design criteria; squeeze-percentage bands cross-read from Parker O-Ring Handbook ORD-5700 Design Charts 4-2/4-3 (verification only); depth = CS - CS x squeeze%
- **Method**: computed
- **Verified against**: computed depth band brackets the published design-chart band for every series

### Assumptions

- Dimensions are for a nominal, unstretched ring at room temperature. Installed stretch reduces cross-section.
- Gland figures are static-application only and assume a nominal ring; they carry no compound, temperature or pressure assumption.
- Dataset scope: A fabricated-dataset negative control is asserted against on every run. EXCLUDED: groove width, corner radius, diametral clearance, back-up ring widths, surface finish, all dynamic glands, the 900-series, and ISO 3601 metric sizes.

**Data last verified**: August 1, 2026

## Common Questions About the AS568-155 O-Ring

### What size is an AS568-155 o-ring?

AS568-155 has an inside diameter of 3.9870 in (101.270 mm) and a cross-section of 0.1030 in (2.620 mm), giving an outside diameter of 4.1930 in (106.510 mm).

### What is the o-ring size tolerance on AS568-155?

The AS568 tolerance on AS568-155 is ±0.0280 in (±0.710 mm) on the inside diameter and ±0.0031 in (±0.080 mm) on the cross-section.

### What groove depth does an AS568-155 o-ring need?

For a static face seal, an 0.103 in cross-section needs a gland depth of 0.0721 to 0.0824 in (1.831 to 2.093 mm), which puts the ring at 20–30% squeeze.

### What o-ring is closest in size to AS568-155?

The nearest AS568 sizes by inside diameter are AS568-045 (3.9890 in ID), AS568-242 (3.9840 in ID), AS568-345 (3.9750 in ID).

## Related pages

- Previous dash number: [AS568-154](https://shopmath.org/o-rings/as568-154.md) — 3.7370 in ID
- Next dash number: [AS568-156](https://shopmath.org/o-rings/as568-156.md) — 4.2370 in ID
- All o-ring sizes: [AS568 o-ring reference](https://shopmath.org/o-rings.md)
- Full size chart: [AS568 o-ring size chart](https://shopmath.org/charts/o-ring-sizes.md)

---

*Source: [ShopMath](https://shopmath.org/o-rings/as568-155) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*