Buick Cascada Tail Light Bulb Size

The Buick Cascada tail light requires a PY21W bulb size for proper installation and function within the rear lighting assembly. Data for the specified bulb covers the range from 2016 through 2019.

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
2016-2019	PY21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament amber bulb with BAU15s bayonet base. 12V, 21W.	PY21W

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Additional Notes

The Buick Cascada uses the PY21W bulb across its entire production run of 2016-2019 for the tail light position.
The PY21W is an ECE-standard bulb, meaning it conforms to European and international automotive lighting regulations rather than SAE standards common in North American vehicles.
The PY21W operates at 12 volts and 21 watts, which is a relatively high wattage for a single-filament bulb and is typical of turn signal applications where brightness and visibility are prioritized.
The bulb produces amber light, which is a factory-specified characteristic of the PY21W rather than a result of a colored lens.
The PY21W uses a BAU15s bayonet base, which has offset pins to prevent incorrect installation. The offset pin configuration distinguishes it from the similarly sized BA15s base, and the two are not interchangeable.
Because the Buick Cascada is a European-origin vehicle sold in North America, its use of ECE-standard bulbs such as the PY21W reflects its design heritage, and direct substitution with common North American bulb types is not supported by the specifications.