Dual-Filament 6V 21/3CP Scooter Taillight Bulb for BAY15d S25 Base

Twin-Filament Rear Bulb for Vintage Scooters and Motorcycles

This 6V 21/3CP twin-filament bulb suits vintage scooters and motorcycles that take a BAY15d S25 base. Use it to replace the taillight or stop/tail bulb in your rear lighting. It is one of the scooter lights & bulbs that deliver a brighter brake light alongside a dimmer running light, which helps keep you visible on the road.

How the Two Filaments Work

The bulb carries two filaments. The brake filament is the brighter of the pair at 21 candlepower, and the tail filament is dimmer at 3 candlepower. Because the two output levels differ, drivers behind you can tell when you are braking versus simply running with your lights on.

Base and Installation

The offset BAY15d bayonet base has a 15mm diameter, so it seats in matching sockets without trouble. As with most vintage scooter bulbs, it drops straight into the existing socket and takes the place of the old bulb with no modifications needed.

Specifications

• Voltage: 6V
• Rating: 21/3CP (21CP stop, 3CP tail)
• Base Type: BAY15d offset bayonet
• Base Diameter: 15mm (0.6")
• Application: Tail / stop / combination rear lighting
• Filaments: 2 (dual-contact base)
• Fits: 6V vintage scooters and motorcycles with a BAY15d (S25) dual-filament tail/stop bulb

Fitment

Fits:

• Vintage Vespa, Honda and other classic 6-volt scooters and motorcycles (check the bulb chart for your model)

How to choose: Confirm your socket matches: BAY15d offset bayonet, 15mm (0.6") base, 6 volt, 21/3CP dual filament.

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