97civic94gsxr

I bought my civic with a HID kit that was already installed and i recently had a bulb go out. I went to 2 autopart stores and both said that they don't have it in stock. I looked them up online and it seems that the 9004 and 9007 look similar and i was wondering which one is going to fit right ? These are the bulbs I was going to get http://cgi.ebay.com/ebaymotors/_Car-...1%7C240%3A1318

CarbonizedDX

I have to ask, were you asking them for a replacement PNP bulb or the halogen bulbs? Cause I know no retail shop will carry PNP anything, let alone OE HID equipment...

Looking similar and being the same is different story.
9004 filament looks like this:

9007 filament looks like this:


Now as you can see the filament is orentated differently between the two which means the reflectors designed for them will be drastically different as well as thier bases are key'd differently...

As for replacing the HID bulb, as long as it's the correct base and has the right connectors (either AMP or KET-B) you should be fine, most HID kit sellers let you specify the bulb type and temp you want at purchase..

tilegend

HIDs dont have filaments, rather they have arcs which are axial so it doesnt matter in differences between 9004 vs 9007. though the problem you stated is true and the problem becomes larger when the original headlamp design was made for transverse filaments (9004) and fitting in hid bulbs which are axial in nature...

CarbonizedDX

Trust me I know, there is a reason I'm using H3C hid bulbs in my H3 applications but the OP never asked about the HIDs nor made it clear exaclty what he was looking for (replacement halogen bulbs or replacement PNP bulbs) thus is why I never brought it up.