Understanding common household light bulb shapes, sizes, and styles is important whether you’re converting outdated incandescent fixtures into energy-efficient ones or using LED bulbs for new-construction applications. Every light bulb has identifying characteristics that are represented by a letter or series of letters and a number; these are known as light bulb codes. The letter or letters in a bulb code indicate either shape or special features such as reflector type. Numbers in a bulb code indicate size in millimeters or eighths of an inch. These codes will tell you if a bulb will fit in your fixture and if it’s the right shape.

For every light fixture or application, there’s going to be a specific bulb or light bulb shape that will fit best and provide the right type of light. If you understand bulb codes, it’s easy to look at a light fixture and know right away what kind of bulb you’ll need.

Let’s talk about light bulb groups, their bulb codes, and what applications those bulbs are typically used for.

Standard/arbitrary (A) bulbs are the most widely used and thought of when it comes to household lighting. These bulbs work well for a variety of applications, such as ceiling lights, lamps, vanity lights, kitchen lights, closet lights, porch light fixtures, and so many more.

Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.

A15 bulb: 15/8 = 1-7/8″ diameter

A19 bulb: 19/8 = 2-3/8″ diameter

A21 bulb: 21/8 = 2-5/8″ diameter

A25 bulb: 25/8 = 3-1/8″ diameter

Most common base types:

Globe (G) bulbs have a full, round shape and are available in various sizes. They can be used for many applications throughout the home, such as foyer lights, kitchen lights, chandeliers, and ornamental fixtures. The most common type is the large G30 bulb, which is used in bathroom and makeup vanities.

Depending on the bulb, numbers in each code can refer to the bulb’s diameter in one-eighths of an inch or in millimeters.

G11 bulb: 11/8 = 1-3/8″ diameter

G14 bulb: 14/8 = 1-3/4″ diameter

G16/G50: 16/8 = 2″ diameter

G60: 60 millimeters = 2-3/8″ diameter

G25/G80: 80 millimeters = 3-9/64″ diameter

G30: 30/8 = 3-3/4″ diameter

Most common base types:

All of the bulbs in these groups resemble the shape of a candle flame and are often referred to as candle bulbs. Conical (C) bulbs are shaped like a cone. Conical angular (CA) bulbs are shaped like a cone but have a bent tip. Blunt-tip (B) bulbs are very similar to C-type bulbs but have more of a torpedo or bullet shape. These bulbs can be used in chandeliers, wall sconces, pendant lights, night lights, decorative light strands, holiday light strands, and other decorative home lighting applications.

Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.

B10 bulb: 10/8 = 1-1/4″ diameter

CA10 bulb: 10/8 = 1-1/4″ diameter

C7 bulb: 7/8 = 7/8″ diameter

C9 bulb: 9/8 = 1-1/8″ diameter

C15 bulb: 15/8 = 1-7/8″ diameter

Most common base types:

BR stands for bulged reflector. Traditionally, the inside surface of an incandescent BR bulb is covered in reflector material that is used to gather and cast a wide beam of light away from the bulb. LED BR bulbs don’t require the reflector material. These bulbs can have a frosted, clear, or patterned dome-shaped lens that diffuses light and provides a gradual fade into nonilluminated areas. BR bulbs also produce less shadows when compared to PAR bulbs. They’re a bit longer than PAR bulbs and tend to protrude from light housings but are used in similar applications, such as track lights, recessed lights, display lights, or can lights.

BR20 bulbs are often referred to as R20 but have the same characteristics of other BR bulb types. The R stands for reflector.

Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.

BR20/R20 bulb: 20/8 = 2-1/2″ diameter

BR30 bulb: 30/8 = 3-3/4″ diameter

BR40 bulb: 40/8 = 5″ diameter

Most common base type:

Multifaceted reflector (MR) bulbs are small in size with a reflective, faceted interior. The facets create a concentrated beam of light that can be displayed in a narrow spot or wide flood beam pattern. Because of the directional light they provide, MR LED bulbs don’t require the facets but often still have them. These bulbs are available in a variety of colors and can be used for many applications, including track lighting, recessed lighting, desk lights, and display case lighting. Many MR bulbs operate on low-voltage wiring systems, which makes them great for outdoor and landscape applications such as driveway lights, path lights, gazebo lights, paver lights, and malibu lights that have weatherproof housings.

Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.

MR11 bulb: 11/8 = 1-3/8″ diameter

MR16 bulb: 16/8 = 2″ diameter

Most common base types:

Tubular (T) bulbs come in a variety of lengths and widths. Depending on their size, these bulbs can be used in applications ranging from chandeliers, wall sconces, and pendant lights to basement and garage troffer light fixtures.

Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.

T7 bulb: 7/8 = 7/8″ diameter

T8 bulb: 8/8 = 1″ diameter

T10 bulb: 10/8 = 1-1/4″ diameter

T14 bulb: 14/8 = 1-3/4″ diameter

Most common base types:

Decorative LED path lights are the perfect gift for dads who want to add an upscale look to their yard. Shade styles include mushroom, frosted glass, offset cone, or hammered cone, and offset linear light heads are also available to direct illumination exactly where it’s needed. These LED path lights can be used for numerous applications, such as garden lights, patio lights, driveway lights, walkway lights, or sidewalk lights. The long-lasting fixtures emit up to 155 lumens of warm white illumination. They’re constructed of powder coated bronze or black aluminum and are weatherproof as well as rust resistant. Each path light comes with a screw-on ground stake.

This easy-to-install, low-profile light mounts directly to a junction box or in a can light housing. It’s perfect for low ceilings, basement, garage, hallway, closet, bathroom, workshop, and shed lighting. The long-lasting LED ceiling light consumes eight times less power than incandescent bulbs with equivalent output. It emits up to 1,100 lumens of natural white or warm white illumination and has a high color-rendering index (CRI) to show the true colors of objects and surroundings. A removable E26/E27 Edison screw base is included along with hardware for mounting to a junction box or in a can light housing.

Help him enhance the look of his boat while increasing nighttime visibility! LED underwater boat lights can be used as transom lights for colorful wakes, attracting fish, or for nighttime swimming and diving. Single-, double-, and triple-lens versions are available, and the underwater lights produce powerful red, green, blue, white, or RGB color-changing illumination. RGB underwater lights are capable of nine dynamic color-changing and single-color modes with an RGB controller and RF remote (sold separately). The LED lights are designed to last 42 times longer than underwater lights with incandescent bulbs.

Do me a favor and imagine that you are in need of suggestions for a Fourth of July party. You head to via Wikipedia

Of course, I’m not talking about snap pops, black cats, m-80s, or even those cool little paper cars that gush sparks, travel four feet, and then burn to death in a microblaze reminiscent of a 1970s action film.

I am talking about the ones that explode up there, the ones you have to tilt your head back to see. That the fireworks explode in the night sky is important because the very act of looking up immediately takes you out of the mundanity that the rest of the holiday will surely deliver – the planning, the decorating, the complications. No more overflowing trashcan with wing sauce-smeared cocktail napkins. No more ordinary stuff.

At the heart of the Fourth of July is a spirit of independence that is, actually, a big deal. When your eyes are on what’s going on at ground level, it can be hard to realize how big a deal ideas like independence and sacrifice are. Once your attention is arrested by the spectacle of fireworks happening up there in the sky, you’re taken out of the everyday and able to reflect on these things, which is important, I think.

2. They are glorious.

“And the rockets’ red glare/ The bombs bursting in air,” goes the song. Did you know that the word “rocket,” in the sense of the combustion-fueled projectile, dates all the way back to 1566? The Oxford English Dictionary notes that rockets have historically been “used for signalling, in maritime rescue, for entertainment, and as a weapon.” Fireworks symbolize communication, violence, and entertainment: A strangely fitting mix for the complex human heart.

The red glare of the rockets in “The Star-Spangled Banner” refers to the bombardment of Fort McHenry in the War of 1812. That the fort was not taken during the battle is indeed glorious, and fireworks are a reminder of the fortitude of the people who fought and suffered to keep America independent in 1776 and again in 1812. Boom. (Literally: boom!)

3. They are beautiful.

So, those are my three reasons that fireworks are the most important part of any holiday festivity: They happen above you; they are glorious; and they are beautiful. I think these are pretty good reasons for making sure you see some fireworks this Fourth of July.

Take a moment out of the hectic festivities to reflect on the spirit of rebellion, creativity, and inspiration that is involved in claiming and defending independence from parties eager to exploit the vulnerable. This is about more than just us. This unites us across time and space. Fireworks reflect the beauty of standing together for what is right, even when it hurts.