There is another option, for my case, the switch is ordinary switch so my default wiring don't have neutral access. What I did is put these switch right before my downlight wiring instead of changing the wall switch. But downside is my ordinary switch have to left it open all the time for these smart switch to be functional. Anyway, I am satisfied with it. Just need the hassel to diy and put the switch on instead of just changing the wall switch. If it don't broken down frequently then shouldn't be a problem.