Features: 1.【Sound output without ultrasonic stabilization is preferred】If the human ear can hear it, it is not ultrasonic. If you can't hear the whistle, how can you be sure that the whistle is going on? Ultrasonic whistles are not suitable for all dogs. Some dogs don't even blink when they hear so-called ultrasound. 2.【It's fun to stop your dog from barking yourself】 Wouldn't it be fun if you train your dog to stop barking? If the dog keeps barking, try to establish a stop command with the whistle and give the dog a command while training the dog. Reward the dog if it stops all movement and is panting. 3.【Patience is the real bond between you and your dog】Some dogs can be extremely uncomfortable with ultrasound. The principle of ultrasound to stop dogs barking is to use ultrasound to make dogs feel uncomfortable. Compressed a-i-r canned dogs/dogs called s-p-r-a-y would be better, but can you be so cruel to dogs? Description: Name: Training Clicker Weight: 50g Material: ABS Size: 7.5 x 2 x 3cm Packing list: 2 x Training Clicker Note: Different displays may cause the color of the item in the picture a little different from the real thing.  Manual measuring,please allow 1~3mm error,thank you.