i have a set of these lookin to go on my car o.z x1 (i think)

i know i need a 20mm spacer but i dont know how it works ????
their call o.z f1 cup 15
rely need a hand with this :/
cheers

i know i need a 20mm spacer but i dont know how it works ????
their call o.z f1 cup 15
rely need a hand with this :/
cheers