38999-type circular connectors · Updated 2026-09-28
38999 Insert Arrangements and Service Ratings Explained
How arrangements are numbered
A 38999 insert arrangement is written as shell size – layout number, for example 25-35. The shell size is the connector size (9 to 25); the layout number identifies the contact pattern within that shell. The same arrangement number means the same contact count, contact sizes and positions, so a circuit design can be reused across finishes and connector types.
Some examples from our J599 Series III range:
| Arrangement | Contacts |
|---|---|
| 11-35 | 13 × size 22D |
| 15-19 | 19 × size 20 |
| 17-26 | 26 × size 20 |
| 21-41 | 41 × size 20 |
| 25-35 | 128 × size 22D |
| 25-61 | 61 × size 20 |
Contact sizes and current
| Contact size | Pin diameter | Rated current |
|---|---|---|
| 22D | 0.76 mm | 5 A |
| 20 | 1.02 mm | 7.5 A |
| 16 | 1.58 mm | 13 A |
| 12 | 2.41 mm | 23 A |
| 10 | 3.20 mm | 33 A |
Size 12 and size 8 cavities can also hold coax, shielded or twinax contacts in the layouts designed for them.
Service ratings
Each arrangement has a service rating that depends on the spacing between contacts. It sets the dielectric withstanding (test) voltage — it is not a working voltage.
| Service rating | Sea level | 21,000 m, mated |
|---|---|---|
| M | 1300 Vrms | 800 Vrms |
| N | 1000 Vrms | 600 Vrms |
| I | 1800 Vrms | 1000 Vrms |
| II | 2300 Vrms | 1000 Vrms |
Choose working voltage with a safety margin below the withstanding voltage, and consider altitude, humidity and contamination in your application.
Finding the right layout
- Count circuits and group them by current.
- Pick the contact size for each group from the table above.
- Look for the smallest shell whose layout fits the mix, with spare contacts for future use.
- Check the service rating against your voltage.
Our series pages list every arrangement with a filter by shell size, contact count and contact size.
