few questions before i install

[320is4dr]

hey guys and gals i just got my billie sports in cause the koni's are shot... so either way i have a few questions that i think i know the answer to but i want reassurence (sorry i'm new to bmw's)

i'm pretty sure the little threaded things screw in to the strut housting, but wtf are the little white plastic circles for. also what would you guys recommend h&r race springs or ie3's ... i'm not worried about it being too bumpy because of my previous car (240sx with coilovers) either way thanks in advance oh and no bump stops are needed with bilsteins right?

[abepark]

sports have built in bump stops yes.

[E30_fiend]

I believe those little white pieces go inside the blue boots to keep it clipped over the shock body.

And as far as springs, either H&R or IE3s. They are technically the same but the IE3s are a bit cheaper than the H&Rs. So if you wanna save some coin, go for the IE3s