The BMW Alpina B7 front inner turn signal requires a 3357NA or 3457NA bulb size, front turn signal uses a 12961 bulb size, and rear turn signal uses a PY21W bulb size. The replacement chart covers 2007 to 2008 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW Alpina B7 rear turn signal positions for both 2007 and 2008 use the PY21W bulb, an ECE-standard single-filament amber bulb rated at 12V and 21W with a BAU15s bayonet base.
The BAU15s base on the PY21W is an offset single-contact bayonet fitting, which prevents substitution with the more common BA15s base used on non-directional bulbs of similar wattage.
The front turn signal (side) position on the BMW Alpina B7 uses the 12961 across both 2007 and 2008, a Philips-numbered miniature wedge bulb in a T10 form factor with a W2.1x9.5d base, rated at 12V and 5W.
The front inner turn signal position differs between model years. The 2007 BMW Alpina B7 uses the 3457NA, a dual-filament wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament. The 2008 model uses the 3357NA, a single-filament wedge bulb rated at 12V and 27W.
Both the 3357NA and 3457NA are T25 wedge bulbs built to ANSI standards for the US and Canadian markets, and both feature natural amber glass rather than a clear envelope with a coated or colored base.
The natural amber glass on the 3357NA and 3457NA produces the amber signal color directly through the envelope, which is a distinct construction from bulbs that rely on an amber-painted lens or housing to achieve the required turn signal color.
Because the 3457NA carries a second filament operating at 7W, it is not a direct drop-in replacement for the single-filament 3357NA used in the 2008 front inner turn signal position, even though both share the T25 wedge form factor and the same 27W primary rating.
The 12961 bulb operates at only 5W, placing it well below the wattage of the other turn signal bulbs in these specifications, which is consistent with its role in a side-marker or supplemental front signal position rather than a primary turn signal.