The 7440NA is the sole bulb type specified for the Lexus RX330, covering both the front and rear turn signal positions across the 2004-2006 model years.
The 7440NA is a single-filament wedge bulb built to the T20 form factor, operating at 12 volts with a power rating of 21 watts.
The "NA" suffix in the 7440NA designation denotes natural amber glass, meaning the amber color is produced by the glass envelope itself rather than by an amber-tinted socket or housing.
As an ANSI-standard bulb, the 7440NA conforms to specifications recognized in both the United States and Canada.
The single-filament construction of the 7440NA means the bulb serves one lighting function per socket, which is consistent with dedicated turn signal applications where a separate circuit handles each function.
Because the same 7440NA bulb is specified for both the front and rear turn signal positions, the RX330 uses a single bulb type across all four turn signal sockets on the vehicle.
The T20 wedge base does not use a metal bayonet or pin configuration; instead, the base of the glass envelope itself acts as the retention and contact mechanism within the socket.
Substituting a 7440 bulb without the NA designation would place a clear-glass bulb in a position where the RX330 specification calls for natural amber glass, which may affect the color output of the turn signal if the lens housing is also clear.