Crimp Contacts, Backshells, Terminals and Solder Sleeves

Updated October 12, 2026

The parts and where they are used

Every one of these parts is cheap compared to the connector it serves, and every one can scrap a harness if it is the wrong revision, plating or size.

For how these are applied and inspected in a finished harness, see the wire harness sourcing guide.

The specifications that govern them, and their status

Nearly all of these moved from military to SAE ownership. The M-prefixed part numbers carried over, so a drawing can still read M39029 or M85049 while the governing document is SAE.

Where both a military and an SAE document exist, as with crimp tools, cite the one your drawing or contract names and do not switch on your own.

Crimp contacts: how M39029 numbers work

An M39029 part number is the specification, a slash sheet and a dash number, as in M39029/56-xxx. The slash sheet identifies the contact family and style; Glenair, for example, lists M39029/56 as a standard duty socket contact used in MIL-DTL-38999 connectors. The dash number then selects size and wire range from the table in that sheet. Because the dash numbers are sheet specific, we do not decode them generically here: read the sheet, or copy the number from the connector manufacturer's contact chart for your exact connector.

Things that matter when buying contacts:

• Match the connector. Contacts are not universal across families, and pin versus socket and contact size have to match the insert arrangement. NASA notes that 38999 connectors are supplied with contacts and that replacements are bought to the contact specification.
• Wire range. A contact barrel is qualified for a wire gauge range. Wire outside that range, or a different stranding, will not crimp to the same pull strength.
• Plating. Contact plating should be compatible with the mating half, and the sheet or manufacturer sets it. Ask before mixing manufacturers in one mated pair.
• Color bands. Contacts carry ink color bands for identification. NASA notes that some contamination-sensitive programs remove them for outgassing control, so check whether your program requires that before the contacts reach the harness shop.
• Spares. Order spare contacts for crimp samples and rework rather than counting exactly one per cavity.

Crimp tools, positioners and inspection

A crimp is controlled by the tool, so the tool is part of the bill of materials. MIL-DTL-22520 covers crimping tools, accessories and inspection gages for removable contacts, terminals, ferrules and splices, and states that tools under it are the only connector assembly devices qualified, procured and issued for military maintenance use.

• Frames and positioners. M22520 hand tools are frames that take a positioner or turret head matched to the contact. The contact manufacturer's data typically names the frame, positioner and selector setting for each contact and wire size; use exactly that combination.
• Inspection gages. The same specification covers inspection gages used to verify the tool. Ask your harness shop how often tools are gaged and how a failed gage check is traced back to the harnesses built since the last good check.
• Pull testing. Destructive pull tests on sample crimps verify the tool, contact and wire combination. The workmanship standard on your order sets the values; our harness page covers IPC/WHMA-A-620 and NASA-STD-8739.4.

If you buy tools for an in-house line, buy them from the tool maker or its authorized distributor with calibration certificates, and include the positioners and gages as separate lines.

Backshells and connector accessories

Backshells are bought separately from the connector. NASA's 38999 application notes say strain relief backshells and seal plugs must be provided separately, and point to the AS85049 selection list. AS85049 is split into slash sheets by connector family and style; one current sheet title, for example, is a backshell extender, category 7, for use on MIL-DTL-38999/44 connectors.

The trade-offs to settle before ordering:

• Function. Strain relief only, environmental sealing, or EMI and RFI shield termination with a band or ring. A shielded cable usually needs a shield termination backshell, not a simple clamp.
• Angle and length. Straight, 45 degree or 90 degree, and the cable entry diameter range for your bundle.
• Material and finish. Match the connector shell class. A nickel connector with a cadmium backshell creates a galvanic couple and, on space hardware, breaks NASA's prohibition on cadmium and zinc plating on EEE parts and associated hardware.
• Torque. Backshell coupling torque is set by the sheet or the manufacturer; your harness shop should record it.

Shell finishes and their temperature and salt spray ratings are covered on our circular connectors page.

Terminals, splices and solder sleeves

Lugs and splices, AS7928. Covers insulated and uninsulated crimp style copper lug terminals and conductor splices for stranded conductors. DoD adopted it on 31 Aug 1999 in place of MIL-T-7928G. Specify stud size, wire range, insulated or not, and plating, and use the crimp tool the terminal sheet names; terminal crimps are as tool-dependent as contact crimps.

Environment resistant splices, AS81824. Covers permanent, crimp style, insulated, environment resistant copper splices. MIL-S-81824 is cancelled and superseded by AS81824. Use these where a splice will see moisture or fluids and must stay sealed.

Solder sleeves, AS83519. These are heat shrinkable sleeves with a solder preform and flux that terminate a cable shield in one heating step. The M83519/1 sheet covers sleeves without a ground lead and M83519/2 covers sleeves with a preinstalled ground lead. Temperature ratings differ by product line: Glenair lists its AS83519/1 and /2 sleeves at -55 C to 125 C, while TE lists 150 C maximum system operating temperature for some of its SolderSleeve series. Pick the line rated for your zone, and confirm whether the ground lead wire type meets your wire specification.

Storage. Solder sleeves contain flux and a solder preform. We found no single published shelf life across these families, so ask the manufacturer for storage conditions and any date limit, and record the lot or date code.

What to put on the purchase order

• Full part number for every contact, backshell, seal plug, lug, splice and solder sleeve, exactly as on the drawing or the connector manufacturer's chart.
• Governing document (AS39029, AS85049, AS7928, AS81824, AS83519, MIL-DTL-22520 or AS22520) and revision where your program controls it.
• Approved manufacturers, and QPL sources where the part is a qualified product.
• Source: manufacturer or its authorized or franchised distributor, with certificates of conformance and lot or date code on each package.
• Quantities that include spares for crimp samples, first article and rework.
• Tooling: frame, positioner and gage part numbers if you are buying tools, with calibration certificates.
• Finish restrictions for backshells and hardware (no cadmium or zinc on space hardware; hexavalent chromium authorization on DoD work where DFARS 252.223-7008 applies).
• Packaging that keeps contact lots separate and labeled; ESD packaging only where the parts go into assemblies with sensitive components.
• Storage or date code limits for solder sleeves and heat shrink items.

Counterfeit and quality risks, and how to receive them

Small interconnect parts are sold in bags of hundreds, which makes them easy to mix, repackage and relabel. The main risks are loose contacts of the wrong sheet or size, open market lots without a traceable manufacturer, and backshells in the wrong finish.

How DFARS applies. DFARS 252.246-7008 (Jan 2023) applies its authorized-source order to electronic parts, defined as integrated circuits, discrete electronic components and circuit assemblies. Contacts, backshells, lugs and solder sleeves are not named. Your program may still require authorized sources for them by contract clause or prime policy, and many defense buyers do. Ask your contracts staff, and read the flow-downs on your PO. Our counterfeit parts avoidance guide covers detection and reporting.

At receiving:

• Check the bag label, certificate and part number agree, and that each bag holds one lot.
• Sample contacts for size, pin or socket, color band and plating appearance; plating should be uniform, without bare or discolored spots at the barrel.
• Fit-check a sample contact in the target connector cavity and confirm retention.
• Confirm backshell finish color and thread size against the connector.
• Check solder sleeve size, ground lead presence on /2 types, and date code.

See receiving inspection and certs and traceability.

How we source contacts, backshells and terminals

We do not hold stock, publish prices or claim to be an authorized or franchised distributor for any manufacturer. We source these parts from the manufacturers and their authorized and franchised distributors, keep lots separate and labeled, and deliver them with their certificates.

• Kits per connector or per harness: connector, contacts with spares, seal plugs, backshell and solder sleeves on one line item list.
• Kits combined with the harness build, cable or a machined bracket on one purchase order.
• Legacy MIL-C and MS part numbers matched to their SAE successors when your engineering approves, and hard to find parts chased under counterfeit-avoidance controls; see obsolete aerospace parts.

Related parts: circular connectors, rectangular connectors, aerospace wire and cable and the electrical parts overview. For harness price drivers, see wire harness cost.

Request contacts, backshells or a connector kit

Send your parts list or connector list through the harness and connector quote form. Listing the connector each contact and backshell goes with lets us match them and catch a wrong size before it ships. A person replies within one business day, and every order ships with a certificate of conformance.

Questions

Related

• Sourcing Aerospace Wire Harnesses and Cable Assemblies
• How to Buy Obsolete Parts Without Buying Counterfeits
• Aerospace Circular Connectors: MIL-DTL-38999 and Its Relatives
• Aerospace Wire and Cable: AS22759, M27500 and Coax

Sources

• NASA NEPP, connector contacts: SAE AS39029 supersedes MIL-C-39029
• EverySpec, MIL-C-39029D cancelled, superseded by SAE AS39029
• Glenair, SAE AS39029 crimp contacts
• EverySpec, MIL-DTL-22520G crimping tools (12 Sep 1997)
• SAE Mobilus, AS22520 crimping tools, wire termination
• NASA NEPP, connector accessories: SAE AS85049 supersedes MIL-C-85049
• NASA NEPP, MIL-DTL-38999 application notes (backshells, seal plugs, color bands)
• DIN Media, SAE AS85049/149 backshell extender for MIL-DTL-38999/44
• EverySpec, SAE AS7928 adoption notice (31 Aug 1999)
• EverySpec, MIL-S-81824 Notice 2, superseded by SAE AS81824
• TE Connectivity, SolderSleeve shield terminators (SAE AS83519)
• Glenair, AS83519/1 and /2 heat shrink termination sleeves