Replacing H4 bulbs with SHORT SERIES bulbs is one of the most common and sensible modifications you can make to a car, especially if it's a few years old. H4 bulbs are special because they have a double filament : a single bulb handles both low and high beams.

This is why the move to LED on this specific format is a huge leap in quality:

1. "Two-in-One" Visual Power

In H4 halogen lamps, when you switch from low beam to high beam, the filament has to heat up and the projection often changes leaving "shadow areas".

• H4 LED: The transition is instantaneous. The dedicated LED chips for the high beams switch to full power in a millisecond, offering a depth of field that halogen cannot physically achieve.

• Lumens: A halogen H4 bulb emits around 1000-1500 lumens. A good LED H4 kit can easily reach 4000-6000 lumens , doubling or tripling the ground illumination.

2. Geometry of the Light Beam

The H4s work a lot on the reflection of the headlight's parabola.

• Modern, high-quality H4 LEDs are designed with a metal shield (dome) that mimics that of the original halogen bulb. This serves to sharply cut the light beam (the so-called cut-off ), avoiding dazzling those ahead and focusing all the light on the road.

3. Less stress on wiring

Cars that mount H4s often have older electrical systems.

• Consumption: An H4 halogen heats up a lot and absorbs around 55/60W .

• Efficiency: LEDs consume around 20/25W . This means less heat inside the headlight (which over time dulls the plastic lenses) and less stress on the connectors and cables, which often tend to cook and melt with halogens.