Thanx for all the information!!!
Is it possible that i've the screw om version en not the bolt on version?
Sorry, i made a (chupid)mistake.
I looked under the car again and it's not my ball joint.
I thought ball joint was the right name for the part.
My technical English is not good enough!
So i need the track rod ends.
Then i've still the same questions.
Can i us aftermarket and change only one site?