Specification: Material: Plastic Size:12.5cm*4cm*2.5cm(4.92*1.57*0.98inch) Color: Black/Yellow Coverage: about 10M Note: Battery (9v stacked battery) is not included. 3 modes 1.Flashlight------ first mode 2.Training Dog---- Middle mode 3. Driving Dog ------ third mode (ultrasonic wave 125dB) The dog driving effect is not good in the following situations: 1. Your own dog, because it knows that the owner will not harm it, 2. Noisy environments, such as downtown areas or roadsides, 3, the dog with the owner outside----dogs know their owner will protect them, trained large dogs---- well-trained, 2. When the battery voltage is too low------the transmit power is low. How to distinguish the Repeller works or not? To tear off a thin strip of paper and send it holding the opposite edge.