The Ram ProMaster City uses the P21W bulb for brake lighting across all documented model years from 2015-2022, making it the dominant bulb type in these specifications.
The P21W is an ECE-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, a base type widely used in European and international automotive lighting applications.
The BA15s bayonet base of the P21W is a single-contact design, which is a critical fitment distinction from the visually similar BA15d double-contact base; the two are not interchangeable despite sharing the same 15mm collar.
The center high mount stop light on the Ram ProMaster City uses the 12961, a Philips-designated miniature wedge bulb of the T10 form factor with a W2.1x9.5d base, rated at 12V and 5W.
The W2.1x9.5d wedge base of the 12961 is a push-fit design, physically distinct from the BA15s bayonet base of the P21W, meaning the two bulb types serve separate sockets and are not interchangeable with each other.
The 12961 operates at 5W, significantly lower than the 21W rating of the P21W, reflecting its role as a supplemental stop light rather than a primary brake light source.
The center high mount stop light specification does not include a 2021 entry, while the primary brake light specification covers all years from 2015-2022 without interruption.