Look on the back side of the wheels. The seller of the other wheels should be able to do the same.

You'll see something like:

8 1/2J x 18H2 ET44

8 1/2 J means 8.5" width
18 H2 means 18" diameter wheel
ET44 means 44mm of offset.

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport