Breakaway collars do work. I've had them tested two ways. The first way, I woke up one morning and my cat was collarless. Eventually I found the collar caught on a nail next to the cat tree. Cat was fine so the collar did its job then. The other time, my nieces were visiting and one of the cats' collars "fell off". My guess is she tried to grab him by it. Moral of the story is the breakaway clasps do their jobs.
