I bought these when I changed mine



front
http://www.ecstuning.com/BMW-E46-330...Pads/ES240588/

rear
http://www.ecstuning.com/BMW-E46-330...Pads/ES240592/

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Looking at the pics I can't really see the difference in the pads, can you measure so we have an exact difference (1-2 mm or what?). Also, why don't you just pull the pads and see if they are the same. It would be weird if po only changed 1/2 pads per wheel since pads come in a set of 4