I believe the ones I bought are 70mm. If you buy eBay aftermarket ones, make sure you select the correct size. These are oems: x4 Genuine BMW 70mm wheel center caps 1 3 5 7 X series - eBay (item 250716275692 end time Apr-22-11 07:35:04 PDT)

or buy the updated design from ecstunning: BMW E53 X5 M62 4.6L > Wheels > View All > ES#1843938 BMW Center Cap (70mm) - 36136783536

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2002 3.0i (DOB: 5/2002)
Mods:
A few...