For the 2012 Lexus IS 250, the low-beam bulb depends on the headlight setup: models with halogen headlights use an H11, while models with HID headlights use a D4S. Confirm the headlight type before ordering, since these low-beam bulbs are not interchangeable.
The high-beam and daytime-running-light applications use a 9005 bulb. For fog lights, the listed fitment is H11 LED. Other useful exterior bulb sizes include 7440A for both the front and rear turn signals, 921 for the reverse lights, and 168 for the parking lights.
Interior applications include a 194 courtesy light bulb, DE3021 dome light bulb, 168 map and interior light bulbs, and a DE3022 trunk light bulb. Verify the existing bulb and vehicle configuration before replacement, particularly for the halogen-versus-HID low-beam setup.