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The standard have the copper core. Works great and less expensive than the platinum coated. Only drawback is you need to change them more often.
HTH.
Here's a pic. http://www.c5forum.com/diy/sparkgr/ngk.jpg
I put the V-power TR55 - standard copper core, cost much less than the platinum or iridium ($25 vs $70+?).
Noticed that one of the platinums I took out had the platinum puck blown off. So you end up paying more for platinum or iridium and chances are the little pucks will fly off around the time you should change the copper cores!