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Lightbulb cap types: Which cap fitting do I need?

There are many ways you can filter our catalogue of light bulbs to find the one you need; by wattage, voltage or price, but we think a good starting place is to select the cap fitting the bulb must have.

The cap fitting is the part of the bulb that connects it to the socket of a light fixture.

In this guide we’ll go through the most common types, their physical sizes and what they’re most often used for.

We understand that the disadvantage of buying online is not physically being able to hold the bulb and compare it to your old one.To help you match your old bulb’s fitting we’ve made a handy downloadable cap size chart. Download our cap guide below and print on A4 paper for a 1:1 scale list. Once you’ve done this hold your bulb against the guide and match like for like.

Download our guide to cap types

10 Popular Lightbulb Cap Types

B22d Lightbulb Cap fitting

Name: Bayonet Cap (BC) or B22d Cap

Size: 22mm diameter

Commonly found: in large household lights

See all B22d Bulbs >

E27 Lightbulb Cap fitting

Name: Edison Screw (ES) or E27 Cap

Size: 27mm diameter

Commonly found: in large household lights

See all E27 Bulbs >

B15 Lightbulb Cap Type

Name: Small Bayonet Cap (SBC) or B15d Cap

Size: 15mm diameter

Commonly found: in small household lights

See all B15d Bulbs >

E14 Lightbulb Cap Type

Name: Small Edison Screw (SES) or E14 Cap

Size: 14mm diameter

Commonly found: in small household lights

See all E14 Bulbs >

G13 Lightbulb Cap Type

Name: G13

Size: 2 pins, 13mm apart

Commonly found: on thick fluorescent tubes

See all G13 Bulbs >

G5 Lightbulb Cap Type

Name: G5

Size: 2 pins, 5mm apart

Commonly found: on thin fluorescent tubes

See all G5 Bulbs >

GU10 Lightbulb Cap Type

Name: GU10

Size: 2 pins, 10mm apart

Commonly found: on spotlights

See all GU10 Bulbs >

GU5.3 Lightbulb Cap Type

Name: GU5.3

Size: 2 pins, 5.3mm apart

Commonly found: on spotlights

See all GU5.3 Bulbs >

E10 Lightbulb Cap Type

Name: Minature Edison Screw (MES) or E10 Cap

Size: 10mm diameter

Commonly found: in chandeliers

See all E10 Bulbs >

E40 Lightbulb Cap Type

Name: Giant Edison Screw (GES) or E40 Cap

Size: 40mm diameter

Commonly found: in halls, factories & workshops

See all E40 Bulbs >

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