Starfield:Nautilus

Bastille Shield Generator
The Bastille shield generators are Nautilus' line of smaller, A class shield generators.

Tower Shield Generator
The Tower shield generators are Nautilus' line of medium, B class shield generators.

Fortress Shield Generator
The Fortress shield generators are Nautilus' line of large, C class shield generators.

Citadel Shield Generator
The Citadel shield generators are Nautilus' line of massive, M class shield generators. These are not typically purchasable in-game.