he PetSafe PUSB-300 is the lightest bark control collar available, weighs only 1 ounce! Great for even the smallest dogs. The Sonic Bark Collar snaps right on to your pets existing collar so he doesn’t have to wear a second collar. The PetSafe PUSB-300 Sonic Bark Collar’s adjustable sensitivity levels allows you to customize it for your dog’s unique bark. To deter barking, it emits a loud sound that startles your dog, disrupting his barking and discouraging him from continuing. While very effective, it is perfectly harmless. Features: At 1.9 cubic inches, it is by far the smallest you can buy. Can be attached to your existing collar (one inch width or less. No need for your dog to wear a second collar. Adjustable sensitivity levels so you can be sure to detect your dogs bark every time. Uses loud but harmless audible sound to deter barking. Limited Lifetime Warranty.