not sure what age car/wheels you have, if the centre cap has the printed badge on it then they are just a tight fit in the centre, if it's the newer one fitted to the roadster with wings moulded in then there are 2 tabs with undercuts that clip into the wheel

hth

Ian

Ian
+4 super sports - 1965
+4 duratec - 2004
3 wheeler - 2012
ARP4
Aero 8
+4 M16