When Does AA Guns Modification 2 Become Available

[MoronicAcid]

I have noticed that AA guns modification 2 is not immediately available on tier VI cruisers. However, it becomes available later. When exactly does it become available?

 

Edit: So apparently, certain modifications are only available in specific slots.

[pmgaudio]

well when you get the cleveland.... it is the second slot upgrade...well one choice anyway... which is kinda redundant as the Clev is SUPERIOR AA to begin with..

but not sure exactly what you mean... it is an upgrade that is avail IMMEDIATELY on ships that have it as an option...

 

 

[MoronicAcid]

My bad, I didn't realize it had to do with a specific slot.