Bought the large collar for my GSD, reviews were mixed so I thought it worth a try. The thoeory is fine but in fact the collar just keeps beeping even when the dog isn't barking so there is no association between unwanted behaviour and being beeped at! Panting or even the slightest movement sets it off which upset me because I was driving and so couldnt relieve my dog of the collar immediately. We went for a walk and left the collar on its own on the back seat of the car, when we returned it was still beeping! Total waste of time and money, don't bother with it!