Artisan Archive

Hi all guys, i got a very important question about crafting items.

I have seen that a (for example) weapon repair tool have 3 optional component items (control unit, energy distributor, etc) and i want to know:

a) its better do it with optional components? (i have make one without and one with components and their % are the same)

b) If their are usefull, what they do to the final prototipe?

c) if their are useless, whythey are there?

Too much thanks.