The coaxial cable assemblies in the MIL-DTL-38999 shell are hermetically sealed in the outer conductor of the female shell.
The circular female connector, either as Bulkhead Feedthrough or 4-hole flange can have a minimum of 4 cable assemblies and currently maximum 12 cable assemblies, but in future probably up to 37 cable assemblies.
The female MIL-DTL-38999 shell can be mounted in the skin of the vacuum chamber and makes the need of hermetically sealed adapters unnecessary.