I should really know the answer to this......
 

......BUT!!!

Standard headlight bulbs in an 04 (54 plate) WRX - what fitment type they?

I know they're single filament. Does this make them H1?

I have an aftermarket HID kit at home, but I know the bulb fitment is wrong (bulb doesn't fit into headlamp assembly). I am keen to fit this kit to the scoob rather than have it gather dust in my garage, and have found a source for a pair of bulbs (in any colour temperature and fitment type) I just need to know what I'm ordering.

Can anyone help please?

Low beam are H1
Main beam are HB3