They are same.
They are interchangeable. Difference between the two :ZFR6K-11 is a standard NGK plug where as IZFR6K-11 is the Iridium version.
SPARK PLUG (IZFR6K11) (NGK) Iiridium should come pre-gapped 1.0-1.1 mm (0.039 - 0.043)
ngk BPMR4A
NGK Insulators's population is 3,272.
Copper: NGK 5858 (XR4); Iridium: NGK 7189 (XR41X).....
NGK-BR8ES or NGK-B8ES
NGK BPM6A
ngk BPMR7A
- ngk ilkar7b11
for a 2.4 ngk-tr55 plug
NGK Insulators was created on 1919-05-05.
use NGK, which is best for Japanese machines. the specs to your plug should be found in your owner's manual. NGK CR9E or CR8E (hotter plug) you could also get CR9EIX (iridium)