Every MIL-DTL-38999 Series III connector is fully described by its part number. Once you can read it, you can spot a mismatched mate, order the right backshell, and cross-reference between Amphenol, Glenair, Souriau and other qualified manufacturers. Here is the structure, using D38999/26WA35SN as the example.
The seven fields in a D38999 part number
| Field | Example | Meaning |
|---|---|---|
| Specification | D38999 | MIL-DTL-38999 circular connector family |
| Slash sheet | /26 | /20 wall-mount receptacle, /24 jam-nut receptacle, /26 straight plug |
| Shell finish class | W | W olive-drab cadmium over nickel, F electroless nickel, M composite electroless nickel, J composite olive-drab cadmium, Z black zinc-nickel |
| Shell size | A | A=9, B=11, C=13, D=15, E=17, F=19, G=21, H=23, J=25 |
| Insert arrangement | 35 | MIL-STD-1560 layout; combined with shell size it fixes the contact count and size |
| Contact gender | S | P pin contacts, S socket contacts |
| Key position | N | N normal; A, B, C, D, E alternate keying to prevent cross-mating |
So D38999/26WA35SN is a Series III straight plug, olive-drab cadmium shell, shell size 9, insert arrangement 35, socket contacts, normal key.
Contact counts for the -35 and -98 inserts
The -35 arrangement is the high-density size-22D layout and by far the most common. The -98 arrangement carries fewer, larger size-20 contacts.
| Shell | -35 insert (size 22D) | -98 insert (size 20) |
|---|---|---|
| 9 (A) | 6 | 3 |
| 11 (B) | 13 | 6 |
| 13 (C) | 22 | 10 |
| 15 (D) | 37 | |
| 17 (E) | 55 | |
| 19 (F) | 66 | |
| 21 (G) | 79 | |
| 23 (H) | 100 | |
| 25 (J) | 128 |
Plug, receptacle and the mating rule
A /26 plug mates with a /20 or /24 receptacle of the same shell size, same insert arrangement, opposite contact gender and the same key position. Finish class does not affect mating, but mixing cadmium and nickel finishes on a mated pair is normally avoided for corrosion reasons.
Which backshell fits?
Series III connectors take MIL-DTL-85049 backshells. The most common are M85049/38 (straight strain relief) and M85049/39 (90° strain relief), ordered by the same shell size number and a finish letter that matches the connector (N for nickel, W for olive-drab cadmium). See our Glenair M85049 backshell stock.
Series I and II equivalents
MS27467 (Series I straight plug) and MS27473 (Series II straight plug) use the same insert arrangements, so an MS27467T15B35S carries the same 37 size-22D socket contacts as a D38999/26WD35SN. The shells and coupling differ, so they do not intermate with Series III.
In stock at Newcastle Industries
We stock D38999/20 receptacles and D38999/26 plugs in shell sizes 9 through 25, in W and F finish classes, plus the matching Glenair backshells and protective covers. Browse the D38999 Series III inventory or send us the part number.
Request a Quote or call (310) 845-1555. Newcastle Industries stocks these parts in Los Angeles and answers quotes within one business day.
