Lexus IS350 Turn Signal Bulb Size

Additional Notes

• The 7440NA and 7440 are both single-filament T20 wedge bulbs rated at 12V and 21W. The key difference is that the 7440NA features natural amber glass, which produces an amber light output without requiring a colored lens or coating, while the 7440 uses clear glass.
• The 7443NA and 7444NA are dual-filament T20 wedge bulbs, each rated at 12V with a 21W primary filament and a 5W secondary filament. The natural amber glass on both types serves the same function as on the 7440NA, producing amber output directly from the bulb.
• All four bulb types across these specifications share the T20 wedge base form factor and operate on a 12V electrical system, which reflects the standard automotive electrical architecture used across these model years.
• For the Lexus IS350, the front turn signal position uses dual-filament bulbs (7444NA or 7443NA) in the 2016-2019 and 2021 model years, while the 2022-2024 and 2006-2009 model years use the single-filament 7440NA in that same position.
• The 7443NA and 7444NA are not interchangeable with the 7440NA or 7440 despite sharing the T20 wedge base, because the dual-filament types carry a second contact point to support the additional 5W filament circuit. Installing a single-filament bulb in a dual-filament socket would leave one circuit non-functional.
• The rear turn signal position on the IS350 uses only single-filament bulbs across all listed model years, alternating between the 7440NA (amber glass) and the clear-glass 7440 depending on the specific year.
• The 7443NA and 7444NA share identical wattage ratings (21W/5W) and the same T20 wedge base with natural amber glass. These two types differ in their internal pin configuration, which means they are not universally interchangeable despite their similar specifications.
• All bulb types listed carry ANSI standardization applicable to the US and Canadian markets, indicating that the specifications reflect North American market fitment for the IS350.