i ordered a hid harness, it was labeled as h2-4 is there a difference between h4-2 and 9003/h4?

 

Borrowed from a quick Google search:

H4 is a European designation; 9003 is a DOT designation. European lights are only legal in the US if they're used off-road or on motorcycles.

I think technically the specification for 9003 bulbs is a little stricter on how well the filament is wound, but it doesn't matter as long as you use a decent bulb.

For all intents and purposes, the bulbs are interchangeable.