I use pcbway. Note that they have a bunch of fronts for the same factory (pcbgogo, for example, is the same as pcbway).
I have confirmed this by ordering a custom pcb with weird specs (color, thickness, etc.) and they were all going thru the same manufacturing steps at the same time, down to the second.
I have confirmed this by ordering a custom pcb with weird specs (color, thickness, etc.) and they were all going thru the same manufacturing steps at the same time, down to the second.