The Lexus IS300 dome light requires bulb size DE3175 or 12961 depending on the specific application. Data for the bulb sizes covers the range from 2001 to 2021.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 12961 is the most frequently specified bulb across the Lexus IS300 dome light data, appearing for the 2016 and 2021 model years in the general dome light position, as well as for both the front and rear dome light positions in the 2017-2019 model years.
The 12961 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W. The wedge base design means the bulb is held in place by tension from the socket rather than by a bayonet or screw mechanism.
The DE3175 is specified for the 2001 Lexus IS300 dome light. It follows the ANSI standard used in the United States and Canada, and it is a festoon-type bulb with a 31mm length that makes contact through metal end caps rather than a base socket.
The festoon format of the DE3175 is physically and electrically distinct from the T10 wedge format of the 12961, meaning the two bulb types are not interchangeable despite both operating on 12V automotive circuits.
The 12961 and DE3175 differ in their base types, physical form factors, and wattage specifications, all of which are determined by the socket design built into each model year's dome light housing.
For the 2017-2019 model years, the front and rear dome light positions share the same 12961 bulb specification, indicating that both positions use identical sockets and wattage requirements within those years.