Please note the product wouldn’t make your dog understand your instructions immediately. You are supposed to train your dog to do so. When the dog is 3 to 7 months old the training effect is the best. A training instruction manual is included to help you on that. With ultrasonic sound the whistle can be also used to drive out vicious dogs around. Adjust the whistle to find the suitable sound for your dog because different dogs have different sound sensitivities. Train your dog with the ultrasonic whistle for recall and barking Control so that you don’t need to shout out loudly. Material: Metal & Plastic.