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.