Types of Lamp 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 Diagram Image Description/Use
Bayonet Cap (BC) B22d 22mm B22d Diagram B22d Image Found in a range of applications, especially domestic
Small Bayonet Cap - double contact (SBC) Ba15d 15mm Ba15d Diagram Ba15d Image Found in a range of applications, especially domestic
Small Bayonet Cap - single contact (SBC) Ba15s 15mm Ba15s Diagram   Found in automotive/machine applications
Miniature Bayonet Cap (MBC) Ba9s 9mm Ba9d Diagram   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 Diagram Image Description/Use
Lilliput Edison Screw (LES) E5 5mm E5 Diagram   Small decorative applications and indicator buttons
Miniature Edison Screw (MES) E10 10mm E10 Diagram   Often found in industrial applications
Candelabra Edison Screw (CES) E12 12mm E12 Diagram   An American cap but often used in Europe especially in candle shaped lamps
Small Edison Screw (SES) E14 14mm E14 Diagram E14 Image Commonly found in a range of domestic applications
Edison Screw (ES) E27 27mm E27 Diagram E27 Image This is the most popular Edison Screw cap and is found in a vast range of applications
Giant Edison Screw (GES) E40 40mm E40 Diagram   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 Diagram Image
T4 (13mm) G5 5mm   T4 Diagram
T5 (16mm) G5 5mm T5 Diagram  
T8 (26mm) G13 13mm T8 Diagram T8 Image
T12 (38mm) G13 13mm T12 Diagram  

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 Diagram Image Description/Use
S12 12mm S12 Diagram S12 Image Two peg fittings at either end of the lamp
S14d 14mm S14d Diagram S14d Image One double oval contact in the middle of the lamp
S14s 14mm S14s Diagram