For the 2001 Subaru Forester, both the low-beam and high-beam headlights use a 9003 bulb. The supplied fitment data does not indicate a separate bulb size for different headlight types or configurations.
Other useful exterior bulb sizes include 1157A for the front turn signals, parking lights, and front side markers. The rear turn signals use 7440A, while the reverse lights use 921. Brake lights are listed as 7443R, and the center stop light uses 912.
Check the original tail-light bulb before ordering: one configuration uses 168 or 917, while another uses 7443R. The license-plate light is listed with either 168 or 917, so compare the existing bulb for the correct option.
Interior locations use DE3175 bulbs for the dome, map, and trunk lights. No fog-light bulb fitment is listed in the supplied data.