The BMW 330i brake light utilizes H21W and P21W bulb sizes according to the provided technical specifications for the vehicle lighting system. Available information covers the period from 2001 through 2018 for the specified automotive components.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 330i brake bulb specifications cover two distinct bulb types across the listed model years: the H21W and the P21W, both rated at 12V and 21W under the ECE standard used in Europe and worldwide.
The H21W uses a BAY9s base, which is an offset pin bayonet fitting. This base type differs from the standard BA15s found on the P21W, making the two bulbs physically non-interchangeable despite sharing the same wattage rating.
The P21W, fitted with a BA15s bayonet base, serves as the brake bulb for the BMW 330i across the 2001-2006 model years in the main brake position, as well as the outer brake position for those same years.
For the 2017-2018 model years, the BMW 330i uses the H21W bulb with an Adaptive designation in the main brake position, indicating integration with the vehicle's adaptive braking or lighting system rather than a conventional static brake light circuit.
The inner brake position on the 2006 330i uses the H21W, while the 2001-2005 model years use the P21/4W in that same position. These two bulb types have different base fittings and filament configurations, so they are not interchangeable with each other.
The P21/4W is a dual-filament bulb rated at 12V with a 21W and 4W filament, using a BAZ15d bayonet base. The offset pin arrangement of the BAZ15d base prevents incorrect installation by ensuring the bulb seats in only one orientation.
The outer brake position on the 330i uses the P21W consistently across the 2001-2006 model years, while the inner brake position transitions from P21/4W to H21W between the 2005 and 2006 model years.
All three bulb types listed in the specifications, the H21W, P21W, and P21/4W, conform to ECE regulations, which govern bulb performance and construction standards across European and many international markets.
The H21W and P21W share the same 21W single-filament output but differ in base type, BAY9s versus BA15s respectively, meaning a socket designed for one will not physically accept the other.
The 2006 330i is the only model year in the specifications where the inner and outer brake positions use different bulb types from each other, with the inner position requiring the H21W and the outer position requiring the P21W.