Why "H11 vs 9005" isn't one question — it's three
November 2019. A distributor sent over a purchase order for 240 bulbs. His spec sheet said, and I quote, "headlight bulbs for the cars in our shop." I didn't ask for the size chart. I checked which number came up most often in his vehicle list, saw 9005, and placed the order.
Three weeks later, the shipment landed. About 60% of the cars on his list took H11, not 9005. Different base — PGJ19-2 versus P20d — physically incompatible. 140 out of 240 bulbs went straight to the returns bin. That order cost me $890 in redo, plus a delayed delivery, plus the kind of relationship damage you can't put a number on.
Since then, whenever someone asks me "H11 or 9005?" I ask them what they're actually doing. Because the honest answer is: it depends. Not in a hand-wavey way. In a "your advice is completely different depending on which of three situations you're in" way.
Here are the three:
- You're replacing a burnt-out bulb — one car, one socket, no upgrade involved
- You're upgrading from halogen to LED or HID — same car, but now fitment gets complicated
- You're buying for a fleet, dealership, or repair shop stock — multiple vehicles, mixed sockets, this is where the real money dies
Each one has a different right answer. And in at least one of them, the instinct most buyers have is exactly backward.
Scenario A: You're replacing a burnt-out bulb
If you landed on "H11 vs 9005" because one of your bulbs died and you're trying to buy a replacement — here's the only move that matters:
Buy by the original spec. Not an upgrade. Not "something better." The exact number stamped on the bulb you're pulling out.
Automakers don't pick bulb types randomly. The base determines where the beam hits the road. Swap in a different spec, and either it won't fit the socket, or — worse — it fits but throws light in the wrong pattern. That's a problem for oncoming drivers, and it's a problem for federal compliance under FMVSS 108, which sets beam-pattern requirements for headlamps sold in the US.
Quick reference, so you don't take my 2019 mistake and make it your own:
- H11 — PGJ19-2 base, around 55W. Usually low beam. Common on many Japanese and Korean models.
- 9005 (HB3) — P20d base, around 65W. Usually high beam.
- 9006 (HB4) — P22d base, around 55W. Usually low beam. Looks a lot like 9005 from across the counter. It isn't.
- H7 — PX26d base, 55W. Very different socket geometry. Common on many European makes.
None of these interchange. The bases are physically different shapes. You cannot "make it fit" without cutting things, and if you're cutting things, you're in trouble.
I keep hammering this because it keeps happening. In my first year on this desk (2017), I watched a colleague pop a 9005 into an H11 housing "just to see." It went in. Sort of. It also aimed the beam straight into the mirrors of oncoming traffic, and we had to eat the return on the whole pallet.
Scenario B: You're upgrading from halogen to LED or HID
This is where decisions actually matter, and where I see the most expensive misunderstandings.
The logic most buyers use: "9005 is brighter than H11, so I'll put a 9005 LED in my H11 housing." That logic doesn't survive contact with a socket.
If your car came with H11 halogen, you buy H11 LED. End of discussion. LED upgrade kits are built to match the halogen base — the emitter is positioned where the halogen filament used to be, so the reflector and projector can do their job. Change the base, and you change that alignment, and the light goes everywhere except the road.
But here's the part buyers miss even when they get the base right: LED bulbs are physically longer than the halogen bulbs they replace.
That extra length matters. Some headlight housings have barely any clearance behind the bulb — you're working through a wheel-well access panel, or there's a dust cover that seals the whole thing. A halogen bulb slides in and the cover goes on. An LED bulb, with its heatsink, driver, and sometimes a small fan, might not clear the cover at all.
We had a run of returns in 2021 where about 30% of LED kits came back with the same note: "doesn't fit." Not the base — the customer had the right base. The bulb was simply too long to seat correctly inside the housing. That's a $400-ish lesson per batch, and it taught us to ask one extra question before every LED sale: how much depth is behind your factory bulb?
If I had to give a rough filter, based on what we see on our end: cars from roughly 2015 onward tend to have more generous housing space, and LED upgrades go smoother. Older vehicles, or anything with a compact projector housing, are hit-or-miss. This is a generalization — I've been surprised in both directions. But if you're on the fence about a specific vehicle, measure first.
One more thing on upgrades: check your local road-use rules before assuming any LED retrofit is street-legal. Rules vary widely by state and country, and "it works" and "it's allowed" are different questions.
Scenario C: You're buying for a fleet or shop stock
This is where I've seen the biggest dollar amounts go up in smoke. Not because fleet buyers are careless — because they're often in a hurry, and "just get a bunch of the common ones" feels reasonable.
It isn't.
A 20-truck fleet might break down like this: 8 trucks need H11, 7 need 9005, 5 need 9006. Buy 200 bulbs of "the most popular type" and you've just ordered 200 bulbs where 60% won't fit anything on the lot. That's the exact shape of the $3,200 order that landed on my desk in 2020 — a truck headlight bulb order that I approved without a proper vehicle-by-vehicle check because the deadline was tight and I "knew" what trucks took.
I didn't know. I assumed.
Here's the process we built after that, and the third time something like this happened I made it non-negotiable:
- Get the VIN or the year/make/model/trim for every vehicle in the order. Not a category, not "the shop's usual trucks." Every one.
- Cross-reference each vehicle against a bulb size chart. If your supplier can't give you one, that's a red flag on its own.
- Count the quantities by bulb type before ordering. Not after. Before.
That's about 15 extra minutes per fleet order. Over the last 18 months we've caught 47 potential mis-orders with it. Most of them would've been small — a handful of wrong bulbs here or there. Two of them would have been five-figure problems.
I can only speak to our own order flow, which runs mostly through mid-sized distributors and shops. If you're doing national fleet contracts with hundreds of vehicles, your process probably needs more layers than mine — a database, or at least a spreadsheet maintained by someone whose only job is to keep it current. The principle is the same, but the stakes scale.
How to tell which scenario you're actually in
Answer three questions:
- Is this for one car with a dead bulb? Scenario A. Buy by the number on the old bulb. Don't upgrade. Don't get creative.
- Is this to make one car see better? Scenario B. Match the base first, then check housing depth. Expect to spend more than you think, and expect to have to measure.
- Are you buying for three or more vehicles? Scenario C. Size chart on every vehicle before the PO goes out. Every time.
If you're stuck between categories — say, one truck with a burnt bulb that you'd also like to upgrade — do C's process first (confirm the size), then B's checks (confirm housing clearance). The order matters.
What I've learned the hard way is that there's no such thing as "the best bulb." There's only the bulb that fits your specific car, in your specific housing, for your specific purpose. Anyone who tells you H11 and 9005 are interchangeable is either guessing or selling whatever's in stock. They aren't interchangeable. I know because I paid $890 to learn it, and I'd rather you didn't.
We build a lot of these size charts for customers through Bulbspan Sourcing — not as a marketing pitch, just because it's the one thing that's prevented more return headaches than any other conversation. If you don't have a chart for your fleet yet, that's the first thing I'd fix.
That pricing and turnaround information reflects what we were seeing in late 2024 and early 2025. If your order is going out in a later quarter, verify current numbers — this market moves, especially with shipping.