CFL and LED Lamp Holder Base Types: G23, G24, E26, E27, E39, E40, T5, T8 Complete Guide
Lamp holder base type is the single most important specification when sourcing replacement or OEM lighting components. An incorrect base type means the lamp will not fit, will not make electrical contact, or will create a safety hazard. This guide covers every major CFL and LED lamp holder base type available from Yoeruyo — G-series pin bases, E-series Edison screw bases, B-series bayonet bases, T-series fluorescent holders, and GU-series twist-lock bases — with pin counts, dimensions, wattage ranges, and application scenarios for lighting OEMs, fixture manufacturers, and maintenance procurement teams.
Lamp Base Type Reference Table
| Base Type | Standard | Pin/Contact | Typical Wattage | Primary Application |
|---|---|---|---|---|
| G23 | IEC 60061 | 2-pin, 23mm spacing | 5W-11W | PL-S CFL, compact fluorescent |
| GX23 | IEC 60061 | 2-pin, 23mm spacing (wider) | 5W-11W | PL-S CFL variant |
| G24d | IEC 60061 | 2-pin, 24mm spacing | 13W-26W | PL-C 2-pin CFL |
| G24q | IEC 60061 | 4-pin, 24mm spacing | 13W-26W | PL-C 4-pin CFL (electronic ballast) |
| GX24d | IEC 60061 | 2-pin, 24mm spacing (twist) | 18W-42W | PL-T 2-pin CFL |
| GX24q | IEC 60061 | 4-pin, 24mm spacing (twist) | 18W-42W | PL-T 4-pin CFL (electronic ballast) |
| E14 | IEC 60061 | Edison screw, 14mm dia | Up to 40W | Small decorative, candelabra |
| E17 | IEC 60061 | Edison screw, 17mm dia | Up to 60W | Intermediate base, appliance lamps |
| E26 | IEC 60061 | Edison screw, 26mm dia | Up to 150W | Standard medium base (North America) |
| E27 | IEC 60061 | Edison screw, 27mm dia | Up to 150W | Standard medium base (Europe/Asia) |
| E39 | IEC 60061 | Edison screw, 39mm dia | Up to 400W | Mogul base (North America HID) |
| E40 | IEC 60061 | Edison screw, 40mm dia | Up to 400W | Mogul base (Europe/Asia HID) |
| B22 | IEC 60061 | Bayonet, 22mm dia, 2-pin | Up to 150W | Standard bayonet (UK, Australia, India) |
| T5 | IEC 60061 | G5 2-pin, 5mm tube dia | 4W-35W | T5 fluorescent tubes |
| T8 | IEC 60061 | G13 2-pin, 8mm tube dia | 15W-58W | T8 fluorescent tubes (standard office) |
| GU5.3 | IEC 60061 | 2-pin, 5.3mm spacing | 20W-50W | MR16 halogen/LED |
| GU10 | IEC 60061 | 2-pin twist-lock, 10mm | 35W-75W | PAR16 halogen/LED spotlight |
| GU24 | IEC 60061 | 2-pin twist-lock, 24mm | 13W-26W | CFL/LED energy-saving (North America) |
G-Series Pin Bases: CFL Compact Fluorescent
G23 and GX23 - PLS 2-Pin CFL
The G23 and GX23 bases are the standard 2-pin bases for PL-S compact fluorescent lamps (5W to 11W). Both use magnetic ballasts and are not compatible with electronic ballast 4-pin holders. Our PLS G23 and GX23 compact fluorescent lamp holders cover the full range of 2-pin PL-S CFL mounting configurations. For the compact 2G7 and 2GX7 pin base formats, see our PLS 2G7 and 2GX7 compact fluorescent lamp holders.
G24d and G24q - PLC 2-Pin and 4-Pin CFL
The G24 base family covers PL-C compact fluorescent lamps (13W to 26W): G24d (2-pin, magnetic ballast) and G24q (4-pin, electronic ballast). The 4-pin G24q base is not interchangeable with the 2-pin G24d base. Our PLC G24d and G24q compact fluorescent lamp holders support both configurations. For the full G24, GX24, G23, and GX23 range, see our G24 GX24 G23 GX23 PLC lamp holders full range.
GX24d and GX24q - PLT 2-Pin and 4-Pin CFL
The GX24 base family covers PL-T compact fluorescent lamps (18W to 42W) used in commercial downlights, troffer fixtures, and high-bay lighting. GX24d is the 2-pin magnetic ballast variant; GX24q is the 4-pin electronic ballast variant.
E-Series Edison Screw Bases
E14 and E17 - Small Edison Screw
Our E14 and E17 small Edison screw lamp holders cover the candelabra (E14) and intermediate (E17) base formats used in decorative fixtures, chandeliers, and appliance lamps. E14 is the European standard small base; E17 is the North American intermediate base.
E26 and E27 - Medium Edison Screw (Standard)
E26 (26mm, North American standard) and E27 (27mm, European/Asian standard) are the most widely used lamp bases in the world. Our E26 E27 E39 E40 Edison screw lamp holders cover medium and mogul base configurations. For the complete E-series range including E10, E12, E14, E17, E26, E27, E39, and E40, see our E-series lamp base complete range.
E39 and E40 - Mogul Edison Screw (HID)
E39 (North America) and E40 (Europe/Asia) are the mogul base formats for high-wattage HID lamps (150W to 1000W) used in street lighting, industrial high-bay fixtures, sports lighting, and large-area floodlighting.
B-Series Bayonet Bases
B22 - Standard Bayonet Cap
The B22 bayonet cap is the standard lamp base in the UK, Australia, India, and many Commonwealth countries. Our B22 BA15 bayonet lamp base holders cover B22d (double-contact standard bayonet), B15d (double-contact small bayonet), and B15s (single-contact small bayonet) configurations.
T-Series Fluorescent Tube Holders
T5 and T8 - Linear Fluorescent
T5 (16mm diameter) and T8 (26mm diameter) are the two standard linear fluorescent tube formats. T8 is the dominant format for commercial office and retail lighting worldwide. Our T5, T8, and PGZ18 fluorescent and halogen lamp holders cover end-cap holders for T5 and T8 fluorescent tubes, as well as PGZ18 double-ended halogen holders.
GU-Series Twist-Lock Bases
Our GU series lamp base holders cover GU5.3 (MR16 bi-pin), GU10 (PAR16 twist-lock spotlight), and GU24 (North American CFL/LED twist-lock) configurations for halogen, CFL, and LED lamp applications.
G-Series Bi-Pin Bases
Our G-series lamp base holders cover G4, G5.3, G9, G12, G13, G23, G24, and G53 bi-pin socket configurations for the full range of low-voltage halogen, HID, and LED lamp applications. For GX10 and GY10 specialty projector and stage lighting applications, see our GX10 and GY10 halogen and HID lamp holders.
2-Pin vs 4-Pin CFL: Critical Compatibility Note
| Pin Count | Base Type | Ballast Type | Interchangeable? |
|---|---|---|---|
| 2-pin | G23, G24d, GX23, GX24d | Magnetic ballast | No - 2-pin and 4-pin are NOT interchangeable |
| 4-pin | G24q, GX24q | Electronic ballast (external) | No - 4-pin lamps require 4-pin holders and electronic ballasts |
Critical: A 4-pin CFL lamp cannot be installed in a 2-pin holder, and vice versa. Always verify pin count when specifying replacement CFL lamp holders.
E26 vs E27: Are They Interchangeable?
E26 (26mm, 120V North American standard) and E27 (27mm, 230V European/Asian standard) are mechanically very similar and lamps can often fit in each other's holders. However, they are not officially interchangeable for OEM fixture manufacturing. Always specify the correct base for your target market voltage standard.
How to Identify an Unknown Lamp Base
- Measure the base diameter - for Edison screw bases, measure the thread diameter in mm (14, 17, 26, 27, 39, or 40mm)
- Count the pins - for pin bases, count the pins (2 or 4) and measure the pin spacing
- Check the lamp marking - the base type is printed on the lamp base or packaging (e.g., "G24q-3", "E27", "GU10")
- Identify the lamp type - PL-S = G23/GX23; PL-C = G24d/G24q; PL-T = GX24d/GX24q; MR16 = GU5.3; PAR16 = GU10
Frequently Asked Questions
What is the difference between G24d and G24q lamp holders?
G24d is the 2-pin base for PL-C CFL lamps used with magnetic ballasts. G24q is the 4-pin base for PL-C CFL lamps used with electronic ballasts. They are not interchangeable - the pin configuration is physically different and the ballast type is incompatible.
Are E26 and E27 lamp holders interchangeable?
Mechanically, E26 and E27 lamps can often fit in each other's holders due to the 1mm diameter difference. However, they are rated for different voltages (E26 for 120V, E27 for 230V) and are not officially interchangeable for OEM fixture manufacturing.
What is the difference between B22 and E27 lamp holders?
B22 is a bayonet cap base (quarter-turn lock) used as the standard in the UK, Australia, and India. E27 is an Edison screw base used in continental Europe and Asia. They are not interchangeable - different physical mounting systems.
What lamp holder do I need for a T8 fluorescent tube?
T8 fluorescent tubes use the G13 bi-pin base (2 pins, 13mm spacing). You need T8 end-cap holders (one at each end of the tube) compatible with the G13 base.
What is the GU24 base used for?
GU24 is a North American twist-lock base designed for energy-efficient CFL and LED lamps, introduced to prevent installation of incandescent lamps in energy-efficient fixtures. Not interchangeable with any Edison screw base.
Conclusion
Yoeruyo supplies the complete range of CFL and LED lamp holders - including G23/GX23, G24d/G24q, E14 through E40 Edison screw, B22 bayonet, T5/T8 fluorescent, and GU series twist-lock holders - with bulk and OEM pricing for lighting fixture manufacturers and maintenance procurement teams.
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