Do I need a white or an amber turn signal?

In North America, amber turn signals are the legal standard for all vehicles. Other drivers recognise amber signals more quickly, and reaction time is reduced by up to 0.3 seconds. Our LEDs automatically handle this requirement, displaying the correct color at the right time. When you're finding a new bulb, you won't need to choose between white or amber LED switchback turn signal lights - the dual-function technology does this for you.

How do these compare physically to OEM 4257 / WT21/7W bulbs?

Equivalent base size and seating depth, designed to match OEM tolerances. LED housing is compact, ensuring proper locking and alignment without looseness or fitment issues.

Does this aftermarket LED replacement bulb with built in resistors get hotter than the OEM bulb?

No, the LED does get hot, but not as hot as an incandescent bulb.

I got my LED with built in resistors and I still have hyper flash why?

Did you start the engine before testing? The vehicle engine must be on and running for the BCM to turn on for the load resistors to be detected. Read the Hyperflash guide & know the details

Do I need a white or an amber turn signal?

In North America, amber turn signals are the legal standard for all vehicles. Other drivers recognize amber signals more quickly, and reaction time is reduced by up to 0.3 seconds compared to red brake lights or other colored signals. Our LEDs automatically handle this requirement, displaying the correct color at the right time. When you're finding a new bulb, you won't need to choose between white or amber LED switchback turn signal lights - the dual-function technology does this for you.

Are LEDs and HIDs better than halogen headlight bulbs?

Both LED and HID bulbs offer major advantages over traditional halogen bulbs. They’re significantly brighter, provide better visibility, and last much much longer. LEDs are more energy-efficient and turn on instantly, while HIDs have a more intense beam that reaches farther down the road. Halogens do come standard on many vehicles, but upgrading to LED or HID is a smart move if you want improved safety, performance, and style.

How do these compare physically to OEM 4257 / WT21/7W bulbs?

Equivalent base size and seating depth, designed to match OEM tolerances. LED housing is compact, ensuring proper locking and alignment without looseness or fitment issues.

Why do I still have hyper flash after Installing Underground Lighting LED turn signal with built in Resistors?

The most common reason is basic mistake many make. Make sure you start the vehicle and let the engine run before testing your turn signal for hyper flash. Starting the engine turns on the BCM so the computer can see the resistance in the bulb.

What is the lifespan of these LED bulbs?

These bulbs are built to last, with a lifespan significantly upto 50X longer than standard halogen bulbs. LED lifespan is 25,000 - 50,000 hours on an average whereas halogen is only 500 to 2000 hours

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SKU: 4257-F150R-A

2021–2023 Ford F-150 STX LED Rear Turn Signal Replacement Bulbs With Built-in Resistor | 3X Rear Visibility

Name: 2021–2023 Ford F-150 STX LED Rear Turn Signal Replacement Bulbs With Built-in Resistor | 3X Rear Visibility
Brand: Underground Lighting
SKU: 4257-F150R-A
Price: 64.99 USD
Availability: InStock
Rating: 4.93 (87 reviews)

$64.99 $69.99

Popular right now
Lots of people have looked at this recently

Weak rear visibility in traffic?

300% brighter than halogen for clearer signalling
Built-in resistor eliminates hyperflash instantly
Advanced cooling extends lifespan up to 10× longer
4257 plug & play, zero wiring required
Designed in the USA, assembled with Japanese components

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Description

Why This Rear Turn Signal Bulb Beats Everything Else

Rear signals have to cut through glare, rain, and other brake lights nearby. Halogen bulbs put out roughly 300 to 400 lumens, which limits how far away drivers can see you. This F-150 rear turn signal bulb delivers 1200 lumens instead, giving following drivers contrast and visibility and helping them react faster.
54 SMD LEDs spread 1200 lumens across a full 360-degree beam, so you're visible from behind and from the side. That matters most during lane changes, braking, and intersections, where side angle visibility makes the difference.
LED bulbs draw less current than halogen bulbs and cause rapid blinking on newer trucks. This Ford F-150 turn signal bulb solves it with a built-in resistor that matches the factory load, restoring a normal flash rate while keeping heat under control through a well-designed circuit.
Excess heat reduces LED efficiency and lifespan. A fan paired with a metal heatsink keeps temperatures steady, so brightness holds, and this bulb runs 15 to 50 times longer than a standard halogen tail light bulb.
This is a direct-fit 4257 bulb with a non-polar CANBUS design, built to work cleanly with your F-150's 12V system. No wiring, no external resistors, no modifications, just a fast, reliable install.
Every bulb is designed in the USA and built with Japanese components for tighter tolerances and better durability. That's what keeps the 1200-lumen output steady and reliable over the long run.
This LED upgrade uses about 90% less power than a halogen bulb and lights up instantly instead of building to full brightness.
Amber is the legal standard for rear turn signal bulbs in most states, and it's the color that gives you the clearest, most recognizable signal on a Ford F-150.
Installation takes about 10 minutes. No splicing, no complicated wiring, just a clean plug-and-play swap.

What's Included

What's Included
Bulbs	2X Amber Leds With Built in Resistors
Warranty	Includes a 1-Year Manufacturer Warranty covering defects under normal use.

Product Information

Function: Rear Turn Signal

LED Chips: 54 SMD LEDs

Variant: 4257

Beam Angle: 360° Coverage

Color: Amber

Cooling System: Fan + Metal Heatsink

Electrical Design: CANBUS, Non-polar, CK Compatible

Voltage: 12V DC

Installation: Plug & Play

BLINKER CIRCUITS: No Resistors Required

Tech Specs

Tech Specs
Wattage	24W
Length	2.4"
Diameter	.83"
Intensity	1200 Lumens

Videos

Warranty Information

This product comes with a 1-year warranty. Check the applicable Terms and Conditions for details.

Installation & Tutorial

Download Installation & Tutorial PDF

Frequently Asked Questions (FAQ)

Do I need a white or amber turn signal for my F-150?

Amber is the legal standard for rear turn signals in North America. Other drivers recognize it faster than white, which shaves real time off their reaction. This bulb comes in amber only, built to meet that standard from the start.

Can I use a 3157 or 7443 bulb instead of this 4257?

No. They may look similar, but the base and electrical fitment are different. Confirm your socket before ordering.

What exactly is included when I order these F-150 rear turn signal LED bulbs?

The package includes two amber LED bulbs with built-in resistors, so you can replace both compatible rear turn signal bulbs at the same time. The product also includes a 1-year manufacturer warranty for defects under normal use.

Will the LED burn or melt the lens of my headlight or taillight?

No, LEDs run cooler than OEM bulbs and will not harm or cause any damage to your wiring harness or housings. And our LEDs have an advanced cooling system, making them efficient and durable with a lifespan of 25k+ hours.

Does our rear brake and turn signal bulb with built-in resistors work on taillights with 2 bulbs in each taillight?

Yes, ours is unique and different from other competitors.
Unlike other brands out there that don't work, ours will. We specially designed the circuit board to work with the BCM.

How to confirm 4257 vs 7443 socket on your truck?

Check one of these:

Owner’s manual (bulb size section)
Remove existing bulb → 4257 = dual contact pins (offset), 7443 = wedge base
Match with OEM spec for front turn signal/DRL circuit

2019 is a split year—both types exist depending on trim

Compatibility

Compatibility
Cross-compatibility	2023 Ford F150 STX – Rear Turn Signal, 2023 Ford F-150 – Rear Turn Signal, 2022 Ford F150 STX – Rear Turn Signal, 2021 Ford F150 STX – Rear Turn Signal, 2022 Ford F-150 – Rear Turn Signal, 2021 Ford F-150 – Rear Turn Signal
Fitments	Turn Signal and Running Light
Circuits	12V
Blinker Circuits	No Resistors Required

Payment & Security

Payment Methods

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5 stars: 84 (97%)
4 stars: 2 (2%)
3 stars: 0 (0%)
2 stars: 0 (0%)
1 star: 1 (1%)

Some of the reviews shown are from related products the merchant grouped with this one.

Very bright.

Great lights

Really wish ford would have done all LED bulbs from the factory. Ordered a set of these front turn signal bulbs and wow, they are bright and work great. No error codes or hyper flashing. Seem very well made too. Took about 20 mins for install. Have a set of the brake/turn bulbs on the way next.

Completely satisfied with these bulbs! Amazing the difference between stock and these. Night and day! For the quality you can’t beat the price!

Dang!

Man these bulbs are way better than any other LEDs I have ever purchased! No hyper flashes, bright, beautiful! I feel sorry for who ever is in front of me when the blinkers are on!

Takes about 20 mins per side to install!

Great lights

I’m impressed with how bright these are!

took 13 days to get here for $6.56 and weighs a little more than a letter.

HI, You picked USPS ground which has no guaranteed time frame . We shipped your order the same day it was placed.
Sometimes USPS takes longer Which is not ideal. However, out of our control. If you were in a rush we offered better shipping options like FedEx ground, 2nd day and UPS options as well.

2021–2023 Ford F-150 STX LED Rear Turn Signal Replacement Bulbs for 3X Rear Visibility| 4257 Amber, Built-in Resistor, No Hyperflash | 300% Brighter 1200LM (PAIR)

2021-2023 Ford F150 STX Amber Rear Turn Signal LED Bulb W/ Built in Resistor No hyperflash (PAIR)

Look great easy to install

Awesome

Great service. Part was just what I needed.

Awesome lights

Very bright priced competitive

Work great

Easy install, no issues yet 👍

2023 F150 STX 4x4

These work great for the rear turn signals! Very bright. Will be ordering the reverse lights next. No hyper flash and no external resistors.

Exactly as described - works great

Purchased three sets of led lights for f150 - brake, front, rear turn signals. Units arrived quickly and exactly as described, well made, looks great. I would purchase again without hesitation.

10/10

Zero hyper flashing and significantly brighter than OEM turn signal lights. Would definitely buy again.

Ford f150 XLT

I'm very impressed with the light front and back very good quality lights i really love it thank you ⭐️⭐️⭐️⭐️⭐️

Excellent functionality, okay quality

The light bulb it self works and looks phenomenally, however this is the second set I have had to purchase in the past 2.5-3yrs. The LEDs will eventually die and cause the bulb to malfunction. The cause of the issue appears to be heat. I hope the ones I purchased this time last longer the last. But I am a return customer because the product is good and I haven’t found a competitor who offers the same plug and play design.

F150 STX LED LIGHT CONVERSION

AMAZING HOW BRIGHT THESE ARE AND SO EASY TO SWAP OUT THOSE DULL HALOGENS

Big improvement.

Easy to swap out forward halogen bulbs on the 2023 F 150 with the new Underground LED’s. Amazing difference in the brightness of these new amber directionals/parking lights. Big difference in daylight brightness.

Excellent plug & play upgrade

These lights are perfect! The construction is solid, and they even have a tiny fan that runs when they're turned on to keep them cool. Brilliant amber color as well. The headlamps look much more cohesive with all LEDs. Would highly recommend.

Super bright and no hyper flash.

These are great modification to make the signal lights are nice and bright now.

2023 F150 front turn signal

Super bright LEDs definitely worth the money very, very easy installation

Good Product

Lights perform exactly as described and installation was very easy.

Front turn signal bulbs

Easy plug and play, and super bright leds. I'm not sure why Ford doesn't include these with the led headlights in their 302a package... but they look great.

LED turn signals 22 f150

Works perfectly super fast shipping

Excellent product

I could tell immediately the lights were high quality. They were simple to install on my 2023 Ford F150 XLT. The LEDs may a huge difference in the amount of light be generated and not having to install resistors are absolutely worth the extra cost. Plug and Play. Great product!!

Absolutely love them

Love the LEDs. They are the perfect fit. They are very bright. And they were labeled for easy installation. Definitely recommend these guys

Easy install

Hyper flash

Bulbs are advertised as no hyper flash but will absolutely cause a random hyper flash. And yes all bulbs are pushed completely into the socket.
Vendor sent a different bulb and fixed the issue.
Great customer service.