15KHz for small dogs, 20KHz for docile dogs, and 30KHz for large and naughty dogs. Suitable for dogs from 6 months old to 8 years old. 3-Level Anti-Bark Frequency: This ultrasonic anti-barking device provides 3 adjustable frequency levels,including 15KHz for small dogs,20KHz for docile dogs,30KHz for large and naughty dogs.
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