For the 2000 Nissan Xterra, both the low-beam and high-beam headlights use a 9004 bulb. The supplied fitment data does not indicate a headlight-type or projector/non-projector variation, so 9004 is listed for both headlight functions.
Fog-light fitment is listed as H3 or H3C, so confirm the existing fog-lamp socket before ordering. The front turn signals use 1156A, while the rear turn signals use 3157A. Brake and tail-light applications use 3057R.
Other listed bulbs include 921 for the reverse lights and 912 for the center stop light. Parking-light fitment may be 194 or 7441, and the front side markers use 194NA. License-plate lighting is listed with either 168 or 917. Interior applications include DE3175 for the dome light and 578 for the map light. Verify the original bulb and socket where multiple options are shown.