For the 2004 Chevrolet TrailBlazer, the supplied fitment data lists a 9005 bulb for the high beam and daytime running light. No low-beam bulb is specified in the available data, so verify the headlamp assembly and existing bulb before ordering a replacement. Fog lights use an 880 bulb.
Other useful exterior fitments include 3757A for the front turn signal and parking light, 194NA for the front side marker, and 3157 for the rear turn signal and reverse light. The brake and tail lights use 3157R. The center stop lamp is listed as LED.
License-plate lighting may use either 2825 or 98. Interior applications include 212-2 for the dome and trunk lights, 194 or 7441 for courtesy, glove-box, and map lights, and 37 for the vanity light. Check the socket and lamp currently installed where multiple options are listed.