Upgrading your tail lights ? You may be wondering if you can swap 3157 and 7443 bulbs. While these bulbs share some similarities, there are key differences that determine compatibility.

This article will break down the socket types, physical characteristics, so you’ll know that a 3157 will not properly fit and function in a 7443 housing (and vice versa). In addition, we'll also take a closer look at the CK socket variants found in both bulb sizes.

What are 3157 and 7443 Bulbs?

About 3157 bulb

The 3157 wedge-shaped bulb is a very common light bulb used in vehicles for turn signals, reverse lights, brake lights, and more.

Some manufacturers change the number when they change some small aspects of the bulb. So you may notice there are 3157LL (long life), 3157A (amber coated), 3157A (high output clear bulb), etc.

Shop 3157 replacement bulbs here >>

About 7443 Bulb

The 7443 bulbs are also common in turn signals, tail lights, and reverse lights for Hondas, Chevrolets, Scions, VWs, Toyotas, and more. Like the 3157, you may see 7443LL or 7443NA variants.

LED upgrade bulbs often advertise themselves as "3157" or "7443" replacements. They'll fit those sockets regardless of small differences between makes. With LED bulbs, you don't need to worry about matching the old bulb's lifespan or color.

Shop 7443 replacement bulbs here >>

But there is one important compatibility check - whether your socket is CK-type or standard. That will determine which LED replacement bulb will physically fit and work correctly.

We'll dig into the details below.

What Are the Differences Between 3157 and 7443?

Bases That Don't Align

The 3157 and 7443 bulbs have different base designs that are not interchangeable. The 3157 has a W2.5x16D base while the 7443 has a W3x16d base. This difference in the base shape and size is the main reason why the two bulb types cannot be substituted for one another.

Different Cross-compatibility

The cross-compatibility also differs between the 3157 and 7443.

The 3157’s cross-compatibility bulb sizes are: 3157, 3157A, 3057, 3155, 3157NA, 4157, 3056, 3356, 3456, 4156, 3047, etc.

The 7443 bulb cross-compatibility bulb sizes are: 7443, 7440, 7444NA, 7443ST and 7443LL. 7441, 7444, 992, T20, W21W, WY21W, W21/5W, etc.

What are the Similarities of 3157 and 7443?

Application

The 3157 and 7443 bulbs can both be used for various rear lighting needs on vehicles, including brake lights, turn signals, backup lights, and more. Their deep red color makes them well-suited for signaling other drivers.

Lighting Technology

These bulb models come with standard halogen lighting. However, LED replacements are available for both 3157 and 7443 bulbs, providing brighter, longer-lasting illumination.

Further Reading: What Are CK Sockets or CK Wiring?

CK indicates where the socket's positive and negative contacts are located. Most vehicles use standard 3157 and 7443 bulb connections. However, some vehicles, like 2005-2013 Toyota Corolla front turn signals, use a 3157CK wiring type bulb.

The CK sockets are also called SCK, SACK, or SRCK. For example 3157CK, 3157SACK, 3157SRCK.

What’s the Difference Between Standard 3157 Vs. 3157 Ck Socket?

CK types and standard sockets look identical. The only difference is the wiring configuration. Specifically, the position of the contacts in the socket.

Normally, standard 3157/7443 sockets have one ground and one power contact on each flat side.

But on the 3157CK or 7443CK type socket, the wiring configuration is changed. They have both ground contacts on one flate side of the socket.

So while 3157 vs 3157CK and 7443 vs 7443CK appear identical externally, and internally, their wiring defines their difference.

Why Should You Care?

This matters if you're looking for LED upgrades. You'll want to confirm the bulb socket type and get the right LED bulbs that are designed for the socket.

A 3157 LED bulb installed in a 3157CK socket will fail due to polarity reversal. The vehicle's fuse may blow to protect it from improper wiring. Or the LED may simply not light up if wired incorrectly.

Some LED bulbs feature special circuitry built into the LED bulbs, allowing it to work for both standard and CK sockets. They function properly regardless of positive/negative orientation.

3157 vs. 7443 Bulb Comparison Table

How to Find the Correct Bulb Size for Your Tail Lights

The tail light bulb you need depends on the make and model of your car or truck.

You can check the owner's manual to find the correct bulb type for your brake lights. The manual will specify exactly which bulb you need.

You can also check the bulb itself - the bulb type is typically printed right on the base. If you see "CK" or "SRCK" on the base, that indicates a CK socket bulb.

If you don't have the manual or can't find the bulb specs, you can look up your vehicle online to find the right bulb size. Here at SEALIGHT, just enter your vehicle's year, make, and model into our vehicle selector tool and we'll show you exactly which bulbs fit your tail lights.

Get 3157 or 7443 LED Bulbs at SEALIGHT

Upgrade your vehicle’s lighting with SEALIGHT’s high-performance 3157 and 7443 LED bulbs. Designed for a perfect fit in most standard sockets, these bulbs deliver brighter, clearer illumination for safer driving and a modern look.

SEALIGHT 3157 LED Backup Reverse Lights (6000K, 1800 Lumens) – Enjoy powerful brightness and crisp white light that enhances visibility when reversing.

SEALIGHT SLJ3 3157/3156 LED Tail & Brake Light Bulbs – Ensure your signals are seen clearly from every angle with durable, long-lasting LEDs.

SEALIGHT J2 7440/7443 LED Backup, Tail & Parking Lights – Versatile bulbs that deliver consistent brightness for both reverse and tail light applications.

SEALIGHT SLJ3 7443/7440 Switchback LED Bulbs for Turn Signals & DRL – Switch effortlessly between white and amber lighting for a clean, dynamic style and improved on-road communication.

No matter your lighting needs—whether it’s tail lights, brake lights, turn signals, or reverse lights—SEALIGHT LEDs provide superior brightness, energy efficiency, and long-term reliability.