Quantity: 3 pieces Adjustable Frequency - You can rotate the adjustable whistle nut to find and lock the appropriate pitch frequency for your puppy from the frequency range, which can easily train your dog to unrestricted commands. Silent Whistle - Use an ultrasonic whistle to train your puppy, it is relatively quiet to the human ear and the dog can hear it 25 meters away without shouting to attract its attention. The expected effect will be best for dogs aged 3 to 7 months. Effective Training - Train your puppy to accept different commands and let your pet follow your instructions, such as recall, sit, come, stop, bark, stay, and potty training. Reasonable Design - The dog whistle is made of stainless steel, coated with a rust-proof protective layer, and is packaged in 3 pieces. It is strong and durable, small and lightweight. The length, including the key ring, is about 8.5 cm.Good quality product