Boslla Bullet B4 3-Color LED Headlight Kit Review

The mode switching is the main reason to consider the Bullet B4. It starts in white mode, then cycles to white/yellow with both LED rows enabled, then yellow, then a strobe / warning-flash pattern using the yellow diodes.

Changing modes is simple: switch the lights off and back on. The harder part is beam pattern. Headlight optics are sensitive to LED position, and a multi-color bulb can change which LED row the housing is seeing.

That means you should install and clock the bulb around the mode you plan to use most. If white mode is aligned correctly, yellow or mixed mode may not be as clean. If yellow mode is aligned correctly, white mode may be less ideal.

That is not really a defect. It is the reality of a multi-color LED design, and it is the main tradeoff that separates this from a normal white-only kit.

If you only plan to use white mode, there are newer white-only LEDs that are easier to recommend. If you actually want the ability to switch between white, blended white/yellow, and yellow output, the Bullet B4 still has a real reason to exist.

The warning-flash mode should be treated carefully. It may be useful in certain off-road, emergency, or stationary situations, but it should only be used where it is legal and safe. Do not use it around normal traffic unless you know it is allowed and appropriate.

In the current chart, the Bullet B4 shows a 4.5 reflector score, 958 lux on reflector low beam, 1842 lux on reflector high beam, and 159 lux of reflector glare. That is still a useful reflector result, especially for an older multi-mode design.

The original version 1.0 article ranked it very highly for its time. White mode measured 5400 on reflector low and 7360 on reflector high, while the white/yellow mode measured 3740 low and 4580 high. The original beam pattern rating was 5.0 stars when the bulb was clocked correctly.

The best part was not just brightness. The small LED chips and good alignment helped white mode look close to a halogen beam shape instead of scattering light everywhere.

The caveat is still important: that clean result applies to the correctly clocked mode. Switching to another mode can shift the beam, so this is a good specialty reflector option, not the safest low-effort reflector recommendation.

In the current chart, the Bullet B4 lands at 498 lux for projector low beam and 498 lux for projector high beam, with a projector score of 4.0. That is usable, but newer projector-focused LEDs have moved ahead of it.

The original projector test looked strong for a halogen-projector upgrade. White mode measured 2700 at the projector low hotspot and 5880 on projector high. Yellow mode measured 2370 at the projector low hotspot and 3490 on projector high.

The typical LED dark spot near the bottom of the projector beam was present, but it was small and on par with many other LEDs. The same clocking issue applies here too: a projector may look good in one mode and less ideal in another.

If color switching matters, the Bullet B4 is worth comparing. If projector brightness is the main goal, DDM Saber Max 75W, GTR Ultra 3, or Hikari Wings / Future are stronger modern choices.

In white mode, we measured the Bullet B4 at about 5750K. That is a cool-white headlight color, but not an extreme blue-white look.

The mixed white/yellow mode is more complicated. It is a blend of the white LED row and yellow LED row, not a true single Kelvin source. We measured around 5500K on one meter and around 4900K on another, so it is best described as a blended white/yellow mode rather than a precise color target.

In pure yellow mode, the color measured around 2950K. That is the mode that makes the Bullet B4 useful for poor weather, dust, snow, fog, or slower backroad driving where a warmer color can be easier on the eyes.

Lumen output was strong in the original review. White mode measured 4210 lumens per bulb, or 8420 lumens per set. Mixed mode measured 9532 lumens per set, and yellow mode measured 3925 lumens per bulb.

Boslla described the Bullet B4 as using Philips LED chips. The small chip size and placement were a big part of why the original white-mode beam looked as controlled as it did.

Power ranged from 26.6 watts to 28.1 watts per bulb depending on the mode. Mixed white/yellow mode used the lowest draw at 26.6 watts, white mode ran at 28.1 watts, and yellow mode used about 27.9 watts.

Temperature was well controlled at 109°F / 43°C with the fan cooling system. Fan noise measured 63 dB, which was not a major issue on the bench and should be hard to notice once installed in most vehicles.

Dimmability and DRL behavior

The original article found the Bullet B4 to be dimmable on a common PWM-style circuit, and on a standard power line it dimmed down to 6.3 volts. The current facts list DRL / high-beam dimmable: Yes, but vehicle-specific behavior can still vary.

CANBUS

The current chart treats the Bullet B4 as CANBUS-friendly, but a decoder may still be needed depending on the vehicle. Bulb-out warnings, flicker, or startup behavior can vary by application, so avoid assuming any LED kit is universal.

Clocking and size

The Bullet B4 offers 1-degree clocking, which is more than a nice extra here. It is almost required because the beam needs to be dialed in carefully, especially if you care about more than one color mode.

For fitment, the original article listed the bulb at 36 mm max width, 34 mm from base to rear, and 37 mm diode-handle length. The removable external driver measured 55 x 30 x 13 mm, so plan where it will sit before closing the headlight.

Boslla provides a 1-year warranty. Estimated pricing is around $110-120, depending on bulb size, seller, and sale timing. At that price, it is not really competing as a cheap budget LED; it is competing as a specialty multi-color LED.

The original conclusion was positive because the Bullet B4 performed well for its time, ran cool, offered useful output in multiple modes, and included unusually flexible 1-degree clocking. The current conclusion is more specific: buy it for white/yellow flexibility, not for maximum white-light output.

If you want a normal white LED and never plan to use the other modes, this is probably not the best buy. If you specifically want white mode, mixed white/yellow mode, yellow mode, and a warning-flash mode in one kit, the Boslla Bullet B4 is still the one that stands out. Just install it around the mode you will use most, and use the warning-flash mode only where legal and safe.

As always, our tests are independent. We publish the lab details and let the results decide whether a product belongs on a shortlist.