October 4, 2022

A Guide on Different Types of Lamp Fittings

The lamp cap or base provides an electrical connection to the lamp and ensures the lamp is held in the correct position. It is essential to know the cap type to identify the lamp.

Below we have listed the most popular fittings; if you can not find the type you are looking for or have any further questions please do not hesitate to call our sales team on +44 800 131 3003 and we will be happy to advise you.

Watch our video guide to some of the most popular light fittings

Bayonet Caps

Bayonet caps are mainly used in Great Britain and are distinctive by their 'push and twist' action to install. There are many variations of a Bayonet Cap including some three pin versions known as B22d-3 found in new build homes and on some high pressure mercury lamps for industrial use.

Please note measurements are taken across the diameter of the bottom of the cap, not including pins.

Name	Product Code/Stock Reference	Diameter	Description/Use
Bayonet Cap (BC)	B22d	22mm	Found in a range of applications, especially domestic
Small Bayonet Cap - double contact (SBC)	Ba15d	15mm	Found in a range of applications, especially domestic
Small Bayonet Cap - single contact (SBC)	Ba15s	15mm	Found in automotive/machine applications
Miniature Bayonet Cap (MBC)	Ba9s	9mm	Found in a range of applications, especially industrial

Edison Screw Cap

Edison Screw Caps take their name from the inventor of the light bulb Thomas Edison and are universally used for a range of applications. The table below shows the most popular caps but other less common types are available including E11, E17, E26 and E39. It typically follows that the larger the cap the greater wattage and heat the lamp can withstand.

Please note measurements are taken across the diameter of the bottom of the cap.

Name	Product Code/Stock Reference	Diameter	Description/Use
Lilliput Edison Screw (LES)	E5	5mm	Small decorative applications and indicator buttons
Miniature Edison Screw (MES)	E10	10mm	Often found in industrial applications
Candelabra Edison Screw (CES)	E12	12mm	An American cap but often used in Europe especially in candle shaped lamps
Small Edison Screw (SES)	E14	14mm	Commonly found in a range of domestic applications
Edison Screw (ES)	E27	27mm	This is the most popular Edison Screw cap and is found in a vast range of applications
Giant Edison Screw (GES)	E40	40mm	Commonly used in commercial 250w+ applications

Tip: It can be difficult to measure exactly the diameter of a cap, especially to the nearest mm, so it is useful to remember that CES fittings are distinctive by their three crests (twists in the fitting), all other Edison Screw fittings have four.

Fluorescent Tubes

Fluorescent tubes typically have two pins at either end but there are exceptions to the rule such as the T12 mono pin. Knowing the pin spacing and wattage of a fluorescent tube is enough to identify the lamp type.

Fluorescent Tube Type	Product Code/Stock Reference	Distance between pins
T4 (13mm)	G5	5mm
T5 (16mm)	G5	5mm
T8 (26mm)	G13	13mm
T12 (38mm)	G13	13mm

Architectural and Strip Light

Architectural lamps either have one main centre contact or two at either end. Strip Lights, often used as picture lights, have two contacts at either end.

Please note the diameter given is the measurement across the bottom of the cap.

Product Code/Stock Reference	Diameter	Description/Use
S12	12mm	Two peg fittings at either end of the lamp
S14d	14mm	One double oval contact in the middle of the lamp
S14s	14mm	Two single oval contacts at either end of the lamp
S15	15mm	Found on strip lights. Two S15 contacts at either end of the lamp

Halogen Capsules

Halogen capsules are found in halogen adaptors where the components are: adaptor base – replaceable capsule – decorative cover. This type of lighting is commonly used in domestic environments.

Linear halogen capsules are frequently used in floodlights and have an R7 cap at either end of the lamp.

Product Code/Stock Reference	Distance between pins	Description/Use
G4	4mm	Used in low voltage display applications
GY6.35	6.35mm	Used in low voltage display applications
G9	9mm	Used in 240v mains applications
R7	7mm	Typically found at either end of linear halogen capsules. Used in floodlights and up-lighters

Halogen and LED

GU fittings typically have two pins and are commonly found on halogen and more recently on LEDs. It follows that the larger the cap the great the wattage and heat the lamp can withstand. Therefore, GU4 and GU5.3 fittings are commonly found on low voltage/wattage lamps and often have a 'push fit' action. GU10 fittings are distinctive by their 'twist and lock' fitting action and are common in domestic applications.

The table below shows the more popular of these fittings; however we stock lamps in many other sizes and types including GY9.5, G22 and Gx38q.

Product Code/Stock Reference	Distance between pins	Description/Use
GU4	4mm	Used in spot lighting; both halogen and LED
GU5.3	5.3mm	Used in spot lighting; both halogen and LED
GU6.35	6.35mm	Used in spot lighting; both halogen and LED
GU10	10mm	Used in spot lighting; both halogen and LED

Compact Fluorescents (CFL)

Fittings for single, double, triple and quadruple turn compact fluorescents vary greatly and can be hideously complex to identify. The table below shows the most popular fittings available for particular types of CFL. We also stock a variety of three pin and special compact fluorescent fittings which our sales team will be happy to advise you with.

Lamp Company Part Code	Product Code/Stock Reference	Description/Use
PLC 2 pin	10 and 13w = G24d-1 18w = G24d-2 26w = G24d-3	Commonly found in commercial applications and some domestic energy saving fixtures
PLC 4 pin	10 and 13w = G24q-1 18w = G24q-2 26w = G24q-3	Commonly found in commercial applications and some domestic energy saving fixtures
PLL 4 pin	2G11	Commonly found in commercial applications and some domestic energy saving fixtures
PLT 2 pin	13w = GX24d-1 18w = GX24d-2 26w = GX24d-3	Commonly found in commercial applications and some domestic energy saving fixtures
PLT 4 pin	13w = GX24q-1 18w = GX24q-2 26, 32 and 42w = GX24q-3	Commonly found in commercial applications and some domestic energy saving fixtures
PLS 2 pin	5, 7, 9,11w = G23	Commonly found in commercial applications and some domestic energy saving fixtures
PLS 4 pin	5, 7, 9,11w = 2G7	Commonly found in commercial applications and some domestic energy saving fixtures