Safe and efficient dog training & behavior aids: dog barking control devices emits an ultrasound of 20~25 KHZ, which exceeds the range of human hearing but can easily lead to the dog's attention without hurting your dog like a dog whistle,safe tocorrect unwanted behavior and stop dog barking or prevent eating unsafe food, effective pet corrector for dogs of all types and sizes of age 6 months to 8 years old sonar heads up to 25ft range effect : this anti barking device with dual heads has higher power and more effective than the single head on the market,this electronic dog whistle equips with 800mah rechargeable battery,provide full charge in 1 to 2 hoursfor about 30 days of regular use Two modes with flashlight ultrasonic dog whistle to stop barking ,Deterrent mode:emit a higher intensity ultrasonic sound while the flashlight flashes to drive the fierce dog away,Training mode: emit a lower intensity ultrasonic sound to assist in dailydog training such as stop excessive barking, fighting, biting, and correct other unwanted behaviors,the flashlight also has a long-bright mode for walking your dog at night Slim design with anti-mistake lock key: this dog barking deterrent devices is slimmer that make it is better fit even in a smaller hand,the independent and clear keys make it easy to use,the anti-mistake lock key will avoid false triggers,also come witha adjustable wrist strap for use outdoor Button pressing with vibration effect : when pressing the button of this ultrasonic dog bark deterrent devices, it will also have a vibration effect, which will bring you a better experience ,and the button light indicator will be red in low power