I was initially a bit dubious about how effective this would be, but thought that for the price it was worth trying. Glad I did. Worked very quickly to reduce barking by my German Shepherd (who would previously bark loudly if anyone was on the phone - not helpful when you are on conference calls!). I am selective when I use it (happy for him to bark to e.g. announce visitors) so just put it on when I need him not to bark - and for that it has worked well. Wondered if the two prongs might be uncomfortable, but I have seen no sign at all that they bother him whilst wearing the collar. Based purely on my personal experience with my own dog