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 to correct 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 hours for 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 daily dog 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 with a 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