For people who have had success, what wavelength has helped you ? 620 ? 630 ? 660 ? Normal Red ?Infrared ?

Hi, sorry if this has been asked before but I can't see too much information from studies and I would like to try this therapy but I don't know which wavelength to choose. I am thinking about buying the 620 nm amber red light from redlight man but if there is a good study which says 660 nm is more likely to work than I would buy that instead. I have seen several people say they bought from smarter lights. I am thinking of avoiding purchasing from them because customs charges will probably be very high to get it to Ireland but if that is the company that helped you, thats great and please mention it in the thread. Thank you.

The one I'm thinking of buying