What’s Single-beam bulb ?
Ordinarily ,We call “Single Bulb” in terms of generating a single beam in every bulb.

What’s double bulb?
Double bulb could be divided into : High/Low (Bi-xenon) and moving bulb, it means the same bulb could generate high、low two different light beam.

what’s the flexible bulb?
The moving bulbs’ only have one light beam in single bulb tube. Its operating principle: though change the position of bulb inside the headlamp. It could generate different light beam in various position. It’s high beam when the bulb is nearby the lamp holder. on the contrary, it’s the low beam once the bulb is situated far from the lamp holder.

what’s the Hi/Lo ? (Bi-Xenon lamp)
Hi/Lo means it has both high and low beams. Its operating principle: By means of lamp holder’s reflection, the light occurred by a group of light beam , after reflection mirror’s reflecting anend., this kind of light source are commonly called it as “high beam”. The other are light beam deflecting, the scintillated light the other group is light formed by a group of beam through lamp holder, first half of mirror reflection, light ray reflected out are diffused adown the ground, never bring glare to the opposite driver, this light source are commonly referred as “Low Beam