And later you pay real money for marginal EXP boosts . <| sep |> I figured this out recently , after being confused . Your first trait level extra good part will only help once you ' re on your second iteration . And your second trait level extra great part will only work when you ' re on your third iteration . In other words , your first trait is used AFTER your first iteration , and your second is used AFTER your second iteration . So on your first time designing a part , you only have average components available , so your extra good slot is useless . BUT , when you come to design that part for the second time , now your good components are available , and selecting your trait will allow you to pick an extra component to add to your design . So you could fill your average slot , your good slot , select your trait and then pick another good component . Also , pay attention to the coloured bars under the slots in the top right . You can fill a slot with any components that has matching colours . You might be able to pick 3 average items over picking a good part if it suits you . But anyways , the main point is you can ' t use your good perk until good parts are available and same for the great perk . The traits don ' t become useful until your second iteration and upEdit it ' s kind of confusing because they coloured the good trait same as average components and placed it on the same line . Same for the next trait . It would be easier to understand if they moved the first trait down so it was beside the good components and coloured it accordingly , and similar for the great trait .