Mazda Miata Back Up Light Bulb Size

Additional Notes

• The Mazda Miata backup light specifications cover model years 1990 through 2005, with two distinct bulb types used across that span.
• The 7440 is a T20 wedge-base bulb, meaning it uses a plastic wedge to secure itself in the socket rather than a metal base with pins. It operates at 12 volts and 21 watts, and carries a single filament.
• The 1156 uses a BA15s bayonet base, a single-pin twist-lock mount common in older automotive applications. It also runs at 12 volts and 21 watts with a single filament.
• Both bulb types share identical electrical ratings of 12V and 21W, but their physical bases are incompatible with each other. A 7440 wedge socket will not accept a 1156 bayonet base, and vice versa.
• The Mazda Miata (1990-1997) uses the 1156 bulb for the backup light position.
• Model years 1999-2005 use the 7440 bulb, reflecting a socket change at some point in the vehicle's production history.
• Both the 7440 and 1156 are ANSI-standardized bulbs recognized in the United States and Canada, meaning they conform to defined performance and dimensional specifications within those markets.
• Because the 7440 and 1156 have different base types despite matching wattage, substituting one for the other without an adapter is not possible.
• The single-filament design of both bulb types is appropriate for backup lights, which require only one function, as opposed to dual-filament bulbs used where two brightness levels are needed.
• The 1998 model year is not represented in the provided specifications.