BRZ Stock HID Bulb Info - D4S
 

From Tire rack, they use the D4S Bulb system. Here is a sample set they have for sale.

PIAA Super Cobalt D4S HID (Pr)

http://www.tirerackwholesale.com/ima...scd4shid_s.jpg

• Low/High beam HID capsule For models with HID lamps.
• Price: $282.00 (pair)
  Estimated Availability: Fewer than 2, Special Order Available
  Manufacturer Part #:19997
• Qty:

Additional Product Information
Overview

Are they a Xenon bulb? If so you should not need to replace them very often.

They are stock HID's to my knowledge. Just putting the info out as much as I can find :)

the only real reason you would change the factory HID xenon bulb (when it's not blown out) is to change the color

i have D4s 5000k, 6000k, and 8000k for those who like that "blueish" look on their car, the bulbs are $90/pair and are direct replacements with 1 year warranty

www.theretrofitsource.com has the best pricing on quality HID bulbs.

Let’s not forget the 5-year warranty on the entire kit. Im Sold, DDM's lifetime warranty is obviously better but what good is lifetime if the company goes out of business haha.

That's just not the best approach. You want your light to be white for visibility. The aesthetic people are emulating when they change bulb temperatures is called chromatic aberration, which is color shift caused by the distance of the cut-off from the lens. Varying degrees of this create a thin boundary layer of blue light which makes the headlights appear blue even though all of the light but the boundary layer are white. Changing a bulb is easier, but the trade-off is that you sacrifice luminosity and visibility.

they have D4S at 5000K color at $60 bucks.

4300k and 6k are good option for car headlights. 6k is bright white with blue tint, providing better view of whats ahead.

Of course brighter is always better, but for some people, like me, where they live in the city and there's tons of street lights, I change my lights out to have that slight blue 6000k tint cause I think it looks good, personal preference.