Standard Bulbs - General Information

Older style bulbs have a metal cap and are available with cap diameters of 7, 9, 15, 20, 21 and 22mm. 7 and 9mm bulbs are generally used in warning lamps, 15mm in side, indicator and brake lights and 15,20,21 and 22mm bulbs in headlamps.

Bulb names show what type of bulb they will be:

  • BA = Bayonet fitting with parallel pins
  • BAY = Bayonet fitting with offset pins (bulbs can only be inserted one way)
  • ES = Edison screw fitting
  • 15 = 15mm diameter metal cap (20 = 20mm, 9 = 9mm, etc)
  • s = Single contact
  • d = Double contact

For example: a BA15s bulb will have a bayonet fitting with parallel pins, a cap of 15mm diameter and is single contact.