Designed for dog training - High pitch, quiet to human ears, but not silent. Adjustable screw for dogs who prefer the quieter or louder setting - , Remember to Lock the Nut after adjusting the volume Could save your dog's life when in danger, ie running toward a busy road. Ultrasonic - but not silent. Train to sit, come, stand, lie down and many more. Encourages interaction and play between dog and owner. Lightweight - can be kept in handbag. Train your dog, puppy to be well-behaved. Lightweight design, perfect size, stylish and practical, easy to carry.