It’s a good question.

Taking this opportunity, I would like to answer what’s h1, h4 and h7 bulbs one by one as below.

Frankly speaking, h1 bulbs are always used as high beam in the cars.

As to h7 bulbs, they are always used as low beam in the cars.

Because h4 bulbs have 2 filament, they can be used as high beam together with low beam.

Meanwhile, the lumens output of h1, h4 and h7 is also litter bit different.

In order to make you clearly what’s h1, h4 and h7 bulbs, I will show you pictures as below.

All of our h1, h4 and H7 bulbs are all top quality and competitive price.