Many customers opt to replace the bulbs that come with their projector headlights with aftermarket bulbs. Many customers mistakenly think that they can replace the bulb with the stock application. In reality, since most projectors convert the stock bulb to a small bulb if they want to replace the bulbs they need to know what bulb the projector uses. Though most projectors use an H3 for the low beam and an H1 for the high beam, there are some exceptions. In order to determine what type of bulbs a projector (and most headlights for that matter) uses, you can check the front of the lens below the appropriate bulb housing. Please be aware that some bulbs have multiple names as follows:
9004 = HB 1
9005 = HB 3
9006 = HB 4
9007 = HB 5
H1 = no other common name
H3 = no other common name
H4 = HB2 = 9003
H7 = no other common name