Xoutpost.com - Euro light help.. Bi Xenon or Halogen.

2 BI-XENON HEADLAMPS HEADLIGHTS BMW X5 E53 E 53 NEW | eBay

That is the BI XENON link for close to 1400$ but the problem is it includes only this

Details:

- Bi-Xenon

- with servo motor for LDR

- without glow discharge lamp

- without bulbs

- without cut-in unit

What is the glow discharge lamp and what do i need it for? What purpose does it hold? Also the cut in unit, what is that? I am sorry these are prob newb questions but some guidance will be great.

i was also comparing those to these 2 HALOGEN H7 HEADLAMPS HEADLIGHTS BMW X5 E53 E 53 NEW | eBay

given they are cheaper.

the real difference between the two is what?

Thanks guys