I have a Tri tronics. It is the add on model that you can not control from your collar remote. I really like it. It has several sound options. It is easliy turned on and off. It runs on a duracell 9 volt. The speaker is pointed away from the dogs ears. Only problem I have had is in snow sometime the snow falls into the speaker and the sound is muffled. I had problem with the back door of the collar flexing but emailed tritronics and they sent me a new one (backdoor). It will also go on any nylon plastic collar. I use mine almost all the time in the tall switchgrass.