The H4 headlight bulb, also marketed as 9003 in many regions, is a dual-beam automotive lighting standard that integrates high beam and low beam functions into a single bulb. Identified by its P43t (P43t-38) bayonet base and three electrical contacts, the H4 format enables instant filament-based beam switching without shutters or solenoids, simplifying headlamp assembly design.
H4 bulbs operate on a 12V passenger-vehicle electrical system and are widely used in cars, SUVs, and light trucks, particularly in compact and older headlamp housings where a single bulb performs both lighting roles. Typical halogen H4 specifications include 60W high beam / 55W low beam, a ~5.0A current draw, and ~1,000–1,700 lumens depending on beam mode, with a warm ~3,000–3,200K color temperature.
Because the H4 bulb does not contain a mechanical shutter, beam pattern and cutoff are fully controlled by the headlight housing optics—either reflector-based or dual-filament–compatible projector designs. This makes filament or emitter positioning a critical factor for glare control and road legality when upgrading to LED or HID.
This Underground Lighting collection includes 3 H4 technology variants, covering LED retrofit, HID replacement, and CANbus HID conversion:
Explore our collection of fog lights and turn signal lights, including switchback styles—use the bulb finder to match your vehicle.
H4 LED Headlight Kit – 60W 12000LM Plug & Play (PAIR)
This is a dual-beam H4 LED replacement kit designed to replicate high and low beam functionality using solid-state LED technology. Light is produced via electroluminescence at a semiconductor p-n junction, eliminating filaments and halogen gas.
- Output: up to 12,000 lumens per pair
- Power draw: 60W system total
- Color temperature: 6000K pure white
- Design intent: plug-and-play installation in H4 / 9003 housings
Proper LED chip placement relative to the original dual filaments is essential to maintain correct beam separation between low and high beam modes. Explore our other forward lighting and headlight options
H4 HID Replacement Bulbs – 3700 Lumens (PAIR)
These are xenon HID arc bulbs designed for vehicles already equipped with H4 HID systems. Light is generated by an electric arc inside a xenon-gas quartz capsule, which requires an external 35W ballast for ignition and regulation.
- Output: approximately 3700 lumens per pair
- Color temperatures: 3000K yellow, 6000K white, 8000K white/blue, 10000K blue
- Use case: direct H4 HID bulb replacement, not a full conversion
These bulbs support visibility-focused and appearance-focused configurations depending on color selection.
H4 / 9003 35W Hi-Low CANbus HID Kit with Halogen High (PAIR)
This is a hybrid H4 HID conversion kit engineered for dual-beam headlamp systems. The low beam operates on xenon HID, while the high beam retains halogen filament operation, preserving OEM high-beam response and legality characteristics.
- Includes: H4 HID bulbs, 35W electronic ballasts, igniters, and CANbus circuitry
- Ignition phase: up to ~23,000V
- Sustained operation: ~85V AC regulated output
- Vehicle compatibility: 12V systems with bulb monitoring
CANbus integration prevents dashboard errors, flicker, and bulb-out warnings common in modern vehicles.
Browse our fog light and turn signal collections, including switchback designs, and confirm vehicle fitment via the vehicle search tool. Compare between HID & LED options or contact Underground Lighting experts for more information; we’re just a click away.
