Lesson I learned today :
Do not lose that funny looking little metal thing that came with your car.
It will be the key for your locking lugnuts. Your dad will call you very very pissed off and embarassed that the car guys had to look through your disgusting car, to not find this important little thing. And they will have to go to the dealership and beg them to take the locking nuts off, drive the car back to the shop to unmount the old tires and mount the new ones.
BUT I have shiny new pretty tires that will last for more miles than my car because my Dad is a rockstar!