Safe and harmless for dogs. Easily controls unwanted barking with ultrasonic sound. Adjustable levels: low, medium, and high ultrasonic levels are available, allowing for adjustment based on your dog's barking situation and size. Waterproof. I bought this new, but because I have multiple dogs, I turned it on once, and some dogs responded while others didn't, so I stopped using it. I've been storing it since then, and it has a few bite marks.