I just buy the brass and plastic type at my local bike shop for about $7 and get a lot better results than “rider back or on your left” . I was riding home and used it when passing someone and when I stopped at a light she came up behind me and said that she was going to get a bell because she had some guy respond poorly to her when she yelled on your left when she passed him. I said he was probably just pissed that you passed him! LOL