Types of Light Bulb Bases

You're probably familiar with Edison-style bulbs, but today, there are also other types of light bulb bases. Let's run down each kind.

Light Bulb Base Sizes Chart

Edison Bases

Edison bases, named after the inventor Thomas Edison, are one of the most ubiquitous and historically significant light bulb base types. These bases employ a screw mechanism that allows the bulb to be twisted into the socket, creating a stable electrical connection that's suitable for a wide range of lighting environments.

Technical Overview and Common Light Bulb Base Sizes

The designation of an Edison base includes an "E" followed by a number, which indicates the diameter of the base in millimeters. This simple yet versatile design has been standardized in several light bulb base sizes to cater to different lighting needs:

  • E12 (Candelabra Base): Typically the smallest of the Edison screw base bulbs, E12 bases have a diameter of 12 mm. These are often found in decorative applications such as chandelier lighting, small lamps, and sometimes holiday lighting strings, where a petite and less obtrusive bulb is desired.
  • E14 (Small Edison Screw Base): Slightly larger than the E12, the E14 has a diameter of 14 mm. It's commonly used throughout Europe and is suitable for many household appliances and smaller lighting fixtures.
  • E17 (Intermediate Base): With a diameter of 17 mm, the E17 base serves a niche between smaller decorative bulbs and larger general-purpose bulbs. It's used in appliances, pendant lights, and refrigeration lighting.
  • E26 (Medium Base): The most common size in North America, the E26 base measures 26 mm in diameter. It's the standard size for most residential and commercial lighting fixtures, accommodating a wide range of bulb types from standard incandescents and LEDs to more specialized styles like globes and reflectors.
  • E39 (Mogul Base): The largest of the standard Edison bases, the E39 has a diameter of 39 mm and is used primarily in commercial and industrial settings. These bases support high-wattage bulbs used in street lamps, high bay lighting, and large-area lighting fixtures where intense illumination is necessary.

Applications and Benefits

Edison screw bases have remained popular due to their ease of use and the reliable contact they provide, which is essential for a stable power supply to the bulb. Here's how different sizes fit into various applications:

  • Versatility: From tiny decorative elements to robust industrial fixtures, Edison bases provide solutions across a spectrum of lighting needs, making them highly versatile.
  • Durability: The screw-in mechanism is simple and durable, allowing for easy installation and replacement without specialized tools or training.
  • Compatibility: Edison bases accommodate a wide range of bulb types, including LED, halogen, and incandescent options. Thus, it is easy to switch to more energy-efficient bulbs without changing fixtures.

Bi-Pin Bases

Bi-pin bases, characterized by their two-parallel-pin design, are a common choice for many modern lighting fixtures. They're known for their ease of installation and stable, secure electrical connections.

Common Types

The designation of bi-pin bases typically starts with a "G," followed by a number indicating the millimeter distance between the two pins. This measurement is crucial for matching the correct bulb to the corresponding fixture.

  • GU5.3: This base type is commonly used in low-voltage applications, such as 12V track lighting or focused beam lights, where precise lighting control is necessary. The pins are 5.3 mm apart, making them compact and ideal for tight spaces requiring directed illumination or spotlighting.
  • GU10: The GU10 is designed for 120V applications and features a twist-lock mechanism that holds the bulb securely in place. This makes the GU10 suitable for higher voltage environments, such as residential or commercial recessed lighting, where stability and ease of replacement are essential. The 10 mm pin spacing also ensures the bulb can support the heavier load of standard voltage requirements.

Design Variations

Bi-pin lamps aren't limited to just single or double-pin configurations but can include several variations, enhancing their adaptability to different electrical and lighting needs:

  • Single Pin (S): Often found in linear fixtures or tube lights, single-pin bulbs are simple in design and are used mainly in commercial or industrial settings.
  • Double Pin (D): This is the standard configuration for many bi-pin bases, providing a balance of easy installation and secure attachment
  • Triple Pin (T) and Quadruple Pin (Q): These are less common but are used in specialized equipment or high-performance lighting fixtures where additional stability or electrical contact is needed.


Bi-pin bases are favored in various settings:

  • Adjustable Lighting: Track lights and adjustable spotlights often use GU5.3 bases because they allow for precise positioning, which is crucial in accent lighting or art displays.
  • Recessed Lighting: The GU10's secure locking design makes it ideal for recessed lighting in homes and businesses, where a stable and reliable light source is necessary.
  • Specialty and Safety Lighting: In areas requiring reliable illumination without frequent maintenance, such as in emergency exits or safety lights, bi-pin bases provide a dependable solution.

Advantages of Bi-Pin Bases

There are several benefits for bi-pin bases:

  • Versatility: The different spacing options between the pins allow for use in various electrical systems and voltages, from low-voltage displays to general household lighting.
  • Durability: Bi-pin bulbs are durable, with pins made of sturdy metals capable of handling frequent switching and varying intensities.
  • Precision: The precise spacing, especially in configurations like GU5.3, allows for excellent control over beam angles and intensity, making these bases ideal for focused lighting scenarios.

Bayonet Bases

Although less common than Edison or bi-pin types, bayonet bases offer unique benefits and features that make them suitable for specific applications. They feature one or more notches on the side of the bulb that fit into corresponding slots in the fixture, allowing the bulb to be locked into place with a simple push-and-twist action. This locking mechanism provides a secure and stable connection, which is particularly advantageous in environments where vibrations or movement might dislodge a screw-in bulb. Bayonet bases are typically marked as:

  • SC (Single Contact): This type of bayonet base features a single point of electrical contact at the bottom of the bulb. Single-contact bayonet bases are often used in directional lamps, such as spotlights or certain types of decorative fixtures, where a secure fit is crucial. but the electrical demands are relatively low.
  • DC (Double Contact): Double contact bayonet bases provide a more reliable electrical connection, making them suitable for robust applications. This type is commonly found in larger or higher-powered lamps, such as those used in industrial settings or outdoor lighting where stability and durability are essential.

Applications and Advantages

Bayonet bases are particularly popular in automotive lighting, portable work lights and certain outdoor lighting fixtures. Their quick-connect and disconnect feature makes them ideal for applications where bulbs must be changed frequently or quickly, such as theatrical lighting or transport applications.

Primary Advantages of Bayonet Bases

By understanding the specific attributes and applications of bayonet bases, commercial buyers can better assess their lighting needs and choose the most appropriate type of bulb base for their fixtures.

  • Stability: The twist-lock mechanism prevents the bulb from loosening due to vibrations or impacts, which is crucial in high-movement environments such as vehicles or industrial machinery
  • Ease of Installation: Installing or replacing a bayonet base bulb is typically quicker and safer, requiring less precision to align the bulb with the socket.
  • Safety: The secure fit of the bayonet base minimizes the risk of electrical shorts due to loose connections, which is particularly important in situations when the bulb is exposed to weather or moisture.
Types of light bulb bases

Benefits of LED Lighting

As the world moves toward more sustainable and efficient energy solutions, LED lighting has become the preferred lighting solution in nearly every application. Let's explore the many benefits of LED technology that make this lighting a superior choice.

Energy Efficiency

LEDs are far more energy-efficient than old-style lighting solutions, consuming up to 90% less power. This translates into significant savings, especially in commercial settings where lighting is a significant operational cost.

Longevity and Durability

LEDs are known for longevity, typically lasting up to 50,000 hours or more. This durability minimizes the need for frequent replacements, thereby lowering long-term maintenance costs. The robust nature of LED bulbs, which are resistant to breakage and immune to vibrations and impacts, makes them ideal for industrial use.

Environmental Benefits

Because LEDs are free from toxic elements such as mercury, which is found in fluorescent lighting, you can reduce the environmental impact when LEDs are disposed of or recycled. Their long life span also means less waste enters landfills. Furthermore, LED lighting is crucial in reducing your carbon footprint since it emits less greenhouse gases due to lower energy consumption.

Versatility in Color and Control

LED technology offers several types of color temperatures and brightness, making it versatile for various applications. You can dim and control LED lights for intensity without losing efficiency, which is essential in settings where mood and atmosphere are important.

Gooseneck and Rustic Lighting

Discovering lighting that combines style and reliability can be challenging. Our gooseneck and rustic lighting solutions offer the ideal fixtures that blend elegant design with dependable performance to meet your exacting standards.

FAQs: Light Bulb Base Types

Below, we've addressed some frequently asked questions about light bulb base types. We're always happy to provide information about products, installation, and industry-related trends.

How Do I Determine the Right Base Type for My Light Fixture?

Check the fixture's specifications or the base of the old bulb you're replacing. The base type is usually marked directly on the bulb or inside the fixture. If necessary, measure the diameter or pin spacing to confirm.

Can I Use a Different Base Type Bulb Than What My Fixture Requires?

No, you must use the bulb that matches the base type of your fixture for safety and functionality. Using an incorrect base can lead to poor electrical connections, bulb instability, or damage to the fixture.

Are LED Bulbs Available in All Base Types?

Yes, LED bulbs are available in nearly all base types and are excellent replacements for incandescent and halogen bulbs due to their energy efficiency and long life span.

What's the Difference Between Single-Contact and Double-Contact Bayonet Bases?

Single-contact (SC) bayonet bases have one contact point at the bottom and are typically used for simpler, single-function lighting. Double-contact (DC) bases have two contact points, allowing for more complex functions like dual-filament configurations in automotive headlights.

How Do I Replace a Bi-Pin Bulb Safely?

First, ensure the power is turned off. Carefully pull the bulb straight out of the socket without twisting. When installing the new bulb, align the pins with the socket and push firmly until the bulb is securely in place.

What Should I Do if My Bulb Base Gets Stuck in the Fixture?

If a bulb base becomes stuck in the fixture, turn the power off. Then, use a rubber grip to gently twist and pull the base out. If it remains stuck, consider using a broken bulb extractor tool or contacting a professional.

Rely on Warehouse-Lighting.com for All the LED Light Bulb Base Type

Whether you're a homeowner who needs an Edison-style bulb or you're responsible for buying industrial lighting that requires other light bulb base types, Warehouse-Lighting has what you need. LED lighting offers substantial cost savings and environmental benefits for any commercial or residential space. Explore our light bulb options or visit our Lighting Application & Resource Center for buying guides, informative articles, and other helpful resources.

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