Is H4-3 the same as H4H?

 

I think its safe to assume not... I don't know the exact difference but usually a letter on an H3/H4 or P21 bulb means its a different wattage. It could look like the same bulb externally but the wattage will be different, which could mean the bulb could melt the housing around it, or just simply burn out or not turn on at all.

 

An H4-3 is a type of HID lamp that will do high and low beam operation. This is a true HID and should also have a ballast and HID wiring setup.

The H4H is a standard halogen bulb. The H4H is just the socket / wattage type.