H11A vs H11B HID Lights: Morimoto XB Bulb Guide

With such a wide variety of vehicles these days running an H11 style bulb, it is no surprise that this is one of the most popular sizes we carry here at TRS. But there is a catch that trips up a lot of people, and it comes down to the difference between H11A and H11B. The Morimoto XB HID bulbs are offered in two versions, H11A and H11B, and picking the right one for your application makes all the difference in your light output. Choose wrong and you can end up with a return wire sitting in the way, which throws a shadow into your beam pattern. In this guide we break down the differences, we show you how the bulb design translates to what you actually see on the road, and we help you pick the correct bulb for your car the first time.

H11A vs H11B HID Lights: Why Two Versions Exist

At first glance the H11A and H11B look nearly identical, and that is exactly why so many buyers grab the wrong one. Both are offered so the Morimoto XB HID bulbs can match different headlight housings. The distinction is small but it matters a lot once the bulb is locked into place. When we set them side by side and look at them straight on, the return wire (that little wire running parallel with the glass) sits in a different spot on each version. That difference is not random. It is tied to the alignment of the locking tabs that surround the base of the bulb.

The H11A bulb has its return wire positioned differently from the H11B.

Because the locking tabs are clocked differently around the base, when you twist and lock the bulb into your headlight, the return wire ends up in a different final position depending on which version you chose. On one it lands one way, on the other it lands somewhere else. That is the whole story in a nutshell, but where it becomes important is how that wire position interacts with the type of headlight you are installing into.

Different locking tab alignment determines how the return wire sits once installed.

Reflector Headlights: When It Does Not Matter Much

If you have a reflector-based headlight, meaning just a normal big chrome reflector like you would find in a basic fog light or a standard reflector headlight, the bulb choice is a lot more forgiving. In a reflector housing the light bounces around the entire reflective bowl, so the exact position of that return wire is not nearly as critical. Generally speaking, we recommend an H11A for reflector applications. If your housing is a simple chrome reflector, you can go with an H11A and not worry about it too much.

That said, if you want to dig into the different bulb brands and options available for these housings, it is worth checking out both Morimoto’s H11A bulb page and the GTR Lighting Ultra Series H11A bulbs so you can compare designs before you buy. Both are solid choices for reflector setups, and seeing the bulbs up close makes the wire placement conversation click a lot faster.

Projector Headlights: Where Bulb Choice Gets Serious

Everything changes once you move to a projector-based headlight. Take a projector unit like the one we pulled from a Nissan. Here you are going to want to make sure you pick the H11B, at least in most cases. The reason has to do with how a projector actually creates its beam. Most of the light inside a projector is deflected off the top of the reflector bowl before it passes through the lens and out onto the road.

Projector-based headlights, like this Nissan unit, generally require an H11B bulb.

When you lock an H11B into a projector, the return wire that runs parallel with the glass ends up on the bottom of the bulb once it is seated inside the projector. That is exactly where you want it. With the wire tucked at the bottom, it stays out of the path of the light that is being deflected off the top of the bowl. If you had chosen the wrong bulb and that wire was sitting up top, it would block a portion of that reflected light and leave you with a shadow or dim spot in your projected beam. That is the single biggest reason bulb choice matters more in a projector than it ever does in a reflector.

How to Identify Which Bulb Your Projector Needs

Here is the quick field test we use. Flip the projector around and look at the back. You will see a big keyhole shape where the bulb locks in. If that keyhole is located in the top left corner, you are looking at a projector that needs an H11B bulb. If the keyhole is anywhere else, you are probably going to need an H11A instead.

A keyhole in the top left corner indicates the projector needs an H11B bulb.

To keep it simple in terms of vehicles, H11B is by far the more common of the two and shows up in most Japanese vehicle projector headlights. H11A is really only used on Kia and Hyundai projector headlights, so it is much less common out in the wild. If you drive something Japanese and it has projectors, the odds are heavily in favor of H11B. If your car is Korean, that is when the H11A comes into play. When you are ready to order, you can grab the H11B XB HID bulbs on TRS and be confident you are getting the right base for a typical projector application.

Beam Output: Seeing the Difference in Person

Talking about wire position is one thing, but nothing beats seeing it lit up. We dropped the correct H11B bulb into a projector and fired it up. The result is a clean, even beam with no interruption. The wire is down at the bottom where it belongs, out of the way of the reflected light, so the projected pattern comes out uniform across the road.

Correctly installed H11B bulb produces even light output without shadowing.

Then we swapped in the H11A, the wrong bulb for this projector, just to show you what a mistake looks like. Now the return wire sits in the path of the light being deflected off the top of the bowl, and you can immediately spot the shadow it casts. That dim spot is exactly the sort of defect people notice and blame on the bulb quality, when in reality it is just the wrong version installed for the housing.

Using the wrong bulb, like an H11A in a projector needing H11B, causes a shadow in the beam.

Putting It All Together

So here is the long story short. Most projector-based headlights, especially anything Japanese, need the H11B bulb. Most projector headlights on Korean cars from Hyundai and Kia need the H11A. And if you are running a reflector-based headlight, you do not need to stress about it too much, so just go with the H11A. Keep that keyhole check in your back pocket and you will avoid the shadow problem entirely.

Summary comparison of H11A and H11B bulb applications — Reflector headlights typically use H11A while most projector headlights need H11B.

If you are building out a complete kit, the bulb is only half the equation. It pairs with a ballast, and if you want to understand how the electronics behind the bulb stack up, our comparison of Denso, Matsushita, and Morimoto ballasts is a great next read. For anyone shopping a full setup, you can also browse the universal HID system options to match your bulbs, ballasts, and harness in one place. Get the bulb version right, get the ballast sorted, and you will have a clean, shadow-free beam that performs the way an HID upgrade should.

Frequently Asked Questions

What is the main difference between H11A and H11B HID bulbs?

The bulbs differ in the position of the return wire and the alignment of the locking tabs around the base, which changes where the wire sits once the bulb is locked into the headlight.

Which bulb should I use for a reflector-based headlight?

For reflector-based headlights, like a normal chrome reflector fog light or headlight, the transcript recommends generally going with an H11A bulb.

Why does bulb choice matter more for projector headlights?

In a projector headlight, most of the light is deflected off the top of the reflector bowl, so if the return wire ends up in the wrong position it creates a shadow or dim spot in the beam pattern.

How can I tell which bulb my projector headlight needs?

Look at the back of the projector for the keyhole shape; if it is in the top left corner, you need an H11B, and if it is located elsewhere, you likely need an H11A.

Which vehicles typically use H11A versus H11B?

H11A is mainly used on Kia and Hyundai projector headlights, while H11B is far more common and used in most Japanese vehicle projector headlights.

Meet the Experts Behind The Retrofit Source

Tyler Jordan – Technical Writer
Tyler works directly with the TRS product R&D team, bringing over a decade of automotive aftermarket lighting experience to every article. An avid enthusiast with hundreds of personal installations under his belt, his content is built on hands-on knowledge from the workbench, not spec sheets.

Caleb Morgan – Marketing Manager
Caleb brings over a decade of automotive lighting industry experience and works with TRS customers daily on the front lines. With hundreds of personal lighting installations and a direct feedback loop from real buyers, his content addresses the questions and problems that actually matter.