Ferrari F355 GTS Back Up Light Bulb Size

The Ferrari F355 GTS back up light requires a P21W bulb size for proper installation and function. Data for the specified component covers the range from 1994 to 1998.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1994-1998	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

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Additional Notes

The Ferrari F355 GTS uses the P21W bulb for the back up light across all listed model years, spanning 1994-1998.
The P21W is an ECE-standardized bulb type, meaning it conforms to European and international automotive lighting regulations rather than SAE standards used in North American markets.
P21W bulbs operate at 12 volts and consume 21 watts, which is typical for single-filament signalling applications such as reverse lights.
The P21W uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width. The single-contact design reflects the bulb's single-filament construction.
Because the P21W is a single-filament bulb, it is dedicated to one lighting function only, distinguishing it from dual-filament variants such as the P21/5W, which serves two functions simultaneously.
The BA15s bayonet base is not interchangeable with BA15d fittings. The BA15d base carries two contacts for dual-filament bulbs, and substituting one for the other in the Ferrari F355 GTS would result in an incompatible fitment.