Ultrasonic Dog Anti-barking Device Pet Dog Barking Deterrent Trainer

They're safe for dogs 5-120 lbs, from 6 months to 8 years old. The ergonomic design fits nicely in your hand, while a carabiner lets you take this ultrasonic dog bark deterrent anywhere. It has sound and ultrasonic modes with a frequency of 25 kHz that's hard for humans to hear.