BUHW has more copper in the metal.
They are interchangeable. Difference between the two :ZFR6K-11 is a standard NGK plug where as IZFR6K-11 is the Iridium version.
8 is hotter than 9 (toolmanx3)
Basically they are for different climate/riding conditions.
heat range. 7 is a "hotter" plug. That means it transfers more heat to the cylinder head during operation.
Yes, Only difference is the plug heat rating. The Plug will run a little colder and may foul easier or more frequent.
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ngk BPMR4A
Copper: NGK 5858 (XR4); Iridium: NGK 7189 (XR41X).....
ngk BPMR7A
NGK-BR8ES or NGK-B8ES
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