Alan

The bulb holder portion of the reflector is different for sure - I expect the rest of the reflector is slightly different too - so no this is not possible.

If you are thinking of an H5 bulb & reflector with H4 lens - the filament orientations are also different between H4 & H5 bulbs and this makes a difference to the optics.

I expect in the end there are more good reflectors around than good lenses - despite the obvious optical quality differences new H5s are not usually any cheaper than H4s (usually more expensive).

Alan

dr bob

The bulbs and holders are different and not interchangeable. Might be an interesting project for HID conversion.

No HID projector conversions yet to fit in the teardrop housing. With good clear casting resin for a plain lens cover, this would seem a logical improvement path.