As the documentation says - functionally the same except DOT put a LOWER maximum lumen output on the source for the US market and put tighter tolerances on filament position presumably to give a more controlled beam pattern.

I have not done a side by side comparison in these lamps. Without a goniometer it would be impossible to quantify the results - one may have a more or less pleasing beam pattern, may seem to put out more total light, etc.

In a nutshell a legal (55/65 watt) H4 is allowed to put out more light but will not necessarily do so. But based on this I'd put H4s in price dependant. But as the article suggests if they meet the H4 as well as HB2 spec they are not allowed to put out more light than the DOT (HB2) maximum.

Eric

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Eric

1985 300SD