Amphenol D38999/20, D38999/24 and D38999/26 are MIL-DTL-38999 Series III shell styles with different mechanical functions. D38999/20 is a flange-style wall-mount receptacle, D38999/24 is a jam-nut panel receptacle, and D38999/26 is a straight cable plug. Selecting between them depends primarily on panel installation, available mounting space and cable-routing requirements—not contact count alone.

Quick Comparison

What Is Amphenol MIL-DTL-38999 Series III?

Amphenol Tri-Start™ TV connectors are rugged circular interconnects designed for aerospace, military, marine and harsh industrial systems. Depending on the configuration, they are available with aluminum, composite or stainless-steel shells and multiple plating options.

The product family supports:

• Crimp, solder and PCB contacts

• Signal and power contacts

• Coax, twinax and triax contacts

• Fiber-optic termini

• Standard and high-density arrangements

• EMI/RFI shielding

• Environment-resistant and hermetic versions

• Shell sizes from 9 through 25

The /20, /24 and /26 codes identify only the basic shell style. Shell material, finish, contact layout, contact gender and key orientation are defined by the remaining characters in the complete part number.

D38999/20 Wall-Mount Receptacle

The D38999/20 is a panel-mounted receptacle with a flange and multiple mounting holes. It provides a fixed connector interface on an equipment enclosure, aircraft panel or bulkhead.

Main characteristics

• Fixed panel receptacle

• Four-hole mounting flange

• Front-panel interface

• Rear crimp-contact wiring

• Available with pin or socket contacts

• Mates with a compatible D38999/26 plug

Advantages

The mounting flange distributes mating and cable loads across the panel. This makes /20 suitable for equipment that experiences repeated connection, vibration or mechanical stress.

It is also convenient when the connector may need to be removed individually without disturbing adjacent panel components.

Limitations

The rectangular flange requires more panel area than a jam-nut receptacle. Four mounting holes and a central connector cutout must also be machined into the panel.

Typical applications

• Aircraft avionics panels

• Military communication equipment

• Radar enclosures

• Vehicle-mounted electronics

• Marine control systems

• Rugged industrial cabinets

One example is D38999/20ME26SN, a 26-position composite wall-mount receptacle with female contacts.

D38999/24 Jam-Nut Receptacle

The D38999/24 is a jam-nut receptacle designed for compact panel installation. Instead of a four-hole flange, it is secured through a circular panel cutout with a large retaining nut.

Main characteristics

• Fixed panel receptacle

• Jam-nut retention

• Compact panel footprint

• O-ring panel sealing

• Available with pin or socket contacts

• Mates with a compatible D38999/26 plug

Advantages

A jam-nut receptacle occupies less rectangular panel space and requires fewer mounting holes than a wall-mount version. It is well suited to densely populated equipment panels where multiple connectors must be installed close together.

The integrated O-ring helps seal the receptacle-to-panel interface when the connector is installed according to the specified panel dimensions and torque requirements.

Limitations

The jam nut requires installation and service access around the panel opening. Panel thickness, cutout geometry, anti-rotation features and mounting direction must be checked carefully.

Typical applications

• Compact avionics enclosures

• UAV electronics

• High-density connector panels

• Radar and sensor modules

• Space-constrained military equipment

• Sealed control boxes

Amphenol also offers reduced-flange derivatives that can reduce the footprint further while retaining compatibility with standard D38999 plugs.

D38999/26 Straight Plug

The D38999/26 is a free-hanging straight plug used on cable assemblies. It connects to either a compatible /20 wall-mount receptacle or /24 jam-nut receptacle.

Main characteristics

• Cable-mounted straight plug

• Self-locking tri-start coupling

• Rear accessory thread

• Available with pin or socket contacts

• Supports backshells and strain relief

• Designed for repeated mating and unmating

Advantages

The /26 plug provides a rugged detachable cable interface. Its self-locking coupling helps resist unintended disengagement caused by shock and vibration.

A wide range of M85049 backshells, cable clamps, shield-termination accessories and protective caps can be used to configure the cable termination.

Limitations

The straight cable exit requires adequate clearance behind the plug. If space is restricted, a right-angle backshell or specialized low-profile cable accessory may be required.

Typical applications

• Aircraft wiring harnesses

• Military vehicle cables

• Radar cable assemblies

• Shipboard wiring

• Sensor and actuator cables

• External equipment interconnects

Examples include:

• D38999/26FD19PN – 19-position male plug

• D38999/26FE35PB – 55-position male plug with B orientation

• D38999/26FJ11SN – 11-position mixed-contact female plug

• D38999/26ME26PN – 26-position composite male plug

• D38999/26WC98SN – 10-position female plug

• D38999/26TB5SN – 5-position female plug with Durmalon finish

Detailed Comparison

How the Connectors Mate

The standard pairing structure is:

• D38999/20 receptacle + D38999/26 plug

• D38999/24 receptacle + D38999/26 plug

D38999/20 and D38999/24 are both receptacle shell styles and do not mate directly with each other.

FAQ

What is the main difference between D38999/20 and D38999/24?

D38999/20 uses a mounting flange and multiple screws, while D38999/24 is retained through the panel by a jam nut.

What does D38999/26 mean?

It identifies a straight cable-mounted plug within the MIL-DTL-38999 Series III family.

Does D38999/20 mate with D38999/24?

No. Both are receptacle styles. They normally mate with a compatible D38999/26 plug.

Is D38999/24 always smaller than D38999/20?

For the same shell size, the jam-nut version generally uses less rectangular panel space. Overall installation clearance still depends on the nut, rear accessories and cable routing.

Can the same D38999/26 plug mate with either /20 or /24?

Yes, provided shell size, insert arrangement, contact gender, orientation and other interface requirements match.

Which option is best for a sealed panel?

Both receptacle styles can support environmentally sealed systems when correctly installed and mated. D38999/24 provides an O-ring panel interface, while D38999/20 sealing depends on the specified flange and panel-sealing arrangement.

Conclusion

Use D38999/20 for a conventional flange-mounted equipment interface, D38999/24 for a compact jam-nut panel installation, and D38999/26 for the mating cable plug. After choosing the shell style, confirm shell size, insert arrangement, contact gender, key orientation, shell material, finish and accessories before ordering.

DataStorageIC supplies Amphenol MIL-DTL-38999 Series III connectors for prototype, maintenance and production requirements. Contact us to check current part-number availability, lead time and quotation requirements.