Ballast Recommendations

Attention: This is an old post (June 2017)! Please see the retrofitting guide for up-to-date ballast recommendations.


I have been reluctant to endorse specific manufactures, but so many people are asking that I will list a few here.

Note that I don’t get kickbacks from any of these sites. A lot of the parts can be obtained cheaper elsewhere (especially if you are not in the US). I have personally ordered from all of the vendors listed on this page, so I feel comfortable recommending them, but do shop around (e.g.  eBay)  if price is a discouraging you from attempting a retrofit.

There are two options for HID retrofits – reuse the stock projector with re-based capsules, or replace it with a full Bi-Xenon1 setup (e.g. E46) that uses D2S bulbs.

Learn more about projector retrofits from this great tutorial at TRS.

After choosing rebase vs projector swap, you’ll also need to choose a wattage – either 35W or 50W. All automotive HID capsules are designed to run at 35w and are rated to last 2000 hours or so at that wattage. Driving a 35w capsule at 55w produces much more light output (+40%), but reduces the lifespan by 50% to 1000 hours or less.

Stock Projector +Retrofit Ballasts

This is the easiest and cheapest option, basically, you install the HID capsule into your existing headlight projector, it fits in like a normal H11 (or H7 in Europe) bulb. Since the projector’s reflector/shield/lens was designed for halogen bulbs, you won’t get a super crisp cutoff or bi-xenon functionality, but it’s essentially plug-and-play aside from drilling one hole in the headlight access door for the pass-through grommet.

Along with your SKBOWE, you need to order a standard HID kit, either 35W or 55W, for the type of low-beam bulb your car is fitted with.

50 Watt Options

Please see the retrofitting guide for up-to-date ballast recommendations.

  • HID50’s ULTRA kit – My personal favorite. I have been using these in my car for nearly 8 years. Have replaced the bulbs 4 times, and the ballasts once (after 5 years, the rated lifespan). Rock-solid dependable and very bright.
  • Morimoto XB55 (AMP) – Everyone seems to love these. high quality, waterproof, reliable products.
  • DDM 55W Slim – Not the highest quality, but a great price and a lifetime warranty. The SKBOWE will run these just fine… You’re spending nearly $100 on the error eliminator so that you can use any brand of ballast, if you don’t mind replacing them every 2 years (for free), the DDMs are a great choice.

The benefits of using the stock projectors are that it is inexpensive, simple, and MUCH brighter than the stock halogen setup.

Downsides are lousy cut-off, sub-optimal beam distribution, and no bi-xenon high beam. The cutoff and distribution can be improved by fitting clear lenses to the factory projectors as the stock lenses are textured to reduce filament shadowing – TRS sells the requisite 3″ ZKW-R lenses here.

cutoff from an H11 retrofit, factory lens

Bi-Xenon Projectors & Ballasts

The Bi-Xenon conversion is a lot more involved, and there are no “easy answers.” Many ways to skin this cat:

  • E46 projectors (salvaged from BWM) are a direct swap – you can remove the P1 factory halogen projector and screw in an E46 bi-xenon projector. Examples this one by forcefed on swedespeed or this one on HID planet. Sourcing genuine E46 projectors is getting more and more difficult, and there have been several (low quality) replica batches produced that work their way to eBay other online retailers. Your best bet is to find actual projectors from a salvage yard – but good luck with that! They are in super high demand. For a retrofit bi-xenon setup, I would recommend going with the Morimoto XB35 (D2S) or Morimoto XB55 (D2S) ballasts for the best performance and lowest EMI, though the back cover might need modification. For an easier fit, go with the AMP version of the ballasts and get a D2S -> AMP adapter.
  • You source salvaged (or new, at $800/ea!) FACTORY bi-xenons, and re-wire them to run off of the halogen circuits but you will still need the SKBOWE. The road-following and self-leveling will not work (this has been discussed ad nauseam), and it’s generally agreed that the quality isn’t great. However, the ballasts are included and are actually integrated into the headlight housing, which makes for a cleaner look. This would require a custom SKBOWE setup, please contact me if you are interested in more information.
  • There have been many custom solutions that get the best projectors using adapter brackets. You’re on your own there!

Advantages going with the bi-xenon retrofit route are that it’s by far the best looking light output, distributed correctly, with more light during high beam and a crisp cutoff.

Downsides are that it’s much more expensive, may require invasive headlight surgery, requires additional wiring for the solenoid, you’re on your own for aiming, and the replacement bulbs are more expensive.

cutoff from an e46 retrofit

After doing a projector swap, be sure to aim your headlight level correctly:



  1. Bi-Xenon means that there is a electromechanical actuator in the projector that moves the shield when you activate the high beams, allowing the HID bulb to illuminate the road like a high beam. This works in parallel with the high beam, so you get much more light down range