my mother got my older brother a whistle 3 for christmas to give him peace of mind when leaving for work, since his husky loves to run and explore and gets past the underground fence even with his collar on due to the fluffiness of his neck. he's been gone for over two hours before and my brother loves his dog more than anything in the world, kaiser is his best friend. it's great and the step tracker on the app is fantastic! it also gives you a notification if your dog goes outside the safe area you set for them. it's a really great device.