Rhino 450= DR8EIX Rhino 660= DPR8EIX-9 They do not have a listing for the new 2008 700 EFI models as yet. FYI. I called an NGK distributor and asked what the difference was between the 2 plugs. They are the same size, thread count, heat range, etc. however the DPR8EIX-9 has an extended tip that is called for on the Rhino 660 and not the 450. More @Wikipedia
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