6V 21/3CP dual-filament S25 taillight bulb showing clear glass envelope, BAY15d offset bayonet base, and dual filaments visible inside for vintage scooter tail and stop lighting 6V 21/3CP dual-filament S25 taillight bulb showing clear glass envelope, BAY15d offset bayonet base, and dual filaments visible inside for vintage scooter tail and stop lighting
Close-up of 6V 21/3CP taillight bulb BAY15d bayonet base showing offset bayonet pins and 6V 3CP voltage rating stamped on the metal base collar Close-up of 6V 21/3CP taillight bulb BAY15d bayonet base showing offset bayonet pins and 6V 3CP voltage rating stamped on the metal base collar
End-on view of 6V 21/3CP taillight bulb base showing two dual-contact pads confirming BAY15d dual-filament bayonet base configuration End-on view of 6V 21/3CP taillight bulb base showing two dual-contact pads confirming BAY15d dual-filament bayonet base configuration
6V 21/3CP dual-filament S25 taillight bulb showing clear glass envelope, BAY15d offset bayonet base, and dual filaments visible inside for vintage scooter tail and stop lighting
Close-up of 6V 21/3CP taillight bulb BAY15d bayonet base showing offset bayonet pins and 6V 3CP voltage rating stamped on the metal base collar
End-on view of 6V 21/3CP taillight bulb base showing two dual-contact pads confirming BAY15d dual-filament bayonet base configuration

CEAB

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

SKU B62W
$2.00
Shipping calculated at checkout.
Description

Replace the taillight or stop/tail bulb on your vintage scooter or motorcycle with this 6V 21/3CP Dual-Filament Taillight Bulb. This S25-style incandescent bulb uses a BAY15d offset bayonet base (15mm / 0.6" base diameter) and features two filaments — a brighter stop filament (21CP) and a dimmer tail filament (3CP) — making it the correct replacement for combined tail/brake light applications on 6-volt electrical systems.

Commonly used in vintage Vespa, Honda, and other classic scooters and motorcycles with 6-volt lighting systems. Use the Scooterworks bulb chart to confirm fitment for your specific model.

Technical Specifications

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

California Prop 65 Warning: www.p65warnings.ca.gov
Product Diagrams
Features
  • Dual-filament: 21CP stop / 3CP tail in a single S25 bulb
  • BAY15d offset bayonet base (15mm / 0.6") for secure, polarity-correct fitment
  • 6-volt rated for vintage scooter and motorcycle electrical systems
  • Clear glass envelope for use with colored lens housings
  • Direct replacement for vintage Vespa, Honda, and other 6V tail/stop applications
Specifications

Voltage: 6V | Rating: 21/3CP | Base: BAY15d offset bayonet (S25) | Base Diameter: 15mm (0.6") | Filaments: 2 | Application: Tail / stop / combination rear lighting
Model Fitments

Vintage Vespa, Honda, and other classic scooters and motorcycles with 6-volt electrical systems using BAY15d (S25) tail/stop bulbs. Use the Scooterworks bulb chart to confirm fitment.
  • Same day shipping for orders placed before 2PM (CST) M-F
  • 30-day return period on eligible items
  • Flat-rate shipping for orders shipped to the 48 Contiguous United States.
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