The BMW Motorcycle K100RS FL front and rear turn signal bulbs utilize a P21W size. The replacement chart covers 1991 to 1992 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the sole bulb type specified for the BMW Motorcycle K100RS FL, covering both the front and rear turn signals across the 1991-1992 model years.
The P21W operates at 12 volts and consumes 21 watts, which is the standard wattage for single-filament automotive signalling applications under ECE regulations.
As a single-filament bulb, the P21W is dedicated to one lighting function per socket, meaning it carries no secondary filament for combined stop or tail duties.
The P21W uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet cap with a 15mm collar width. The single-contact design corresponds directly to the bulb's single-filament construction.
The P21W is governed by ECE standards, giving it recognized fitment across European and worldwide markets rather than being limited to a regional specification.
The front and rear turn signal positions share an identical bulb specification on the K100RS FL, meaning the same P21W unit is interchangeable between both locations on the motorcycle.