This is a tiny dynamic microphone preamp PCB, with various additional options.
The PCB itself is complete except for the two transistors, which are supplied but not fitted.
It can be fitted in an inline casing (listed separately). This is a commonly available inline XLR attenuator, which has an easily dismantled case with XLR plug and socket for inline usage.
That can be bought from me, or you can buy these from many sources. The built PCB, with transistors fitted, could also be used in any other casing as you prefer, or be built in to equipment or even possibly fitted inside the body of a dynamic mic, to increase the output level.
Note that these are only suitable for dynamic or other similar non-powered microphones, and the preamp requires phantom power to operate, from whatever mic interface or mixer etc. it is being used with.