This plug in really work s. We have a ten week old Cocker spaniel puppy who literally howled whenever he was left alone. we have had had Cocker’s in the past so we are used to their perseverance of character however this little pup had us shattered. Plug in worked the first night we used it the pup settled in his crate for eight hours overnight and is so chilled out. Our older dog appears more relaxed as well.