Features: 1. Made of high quality, durable and effective to use. 2. Make sounds through the flow of air, no need battery, very convenient. 3. This item designed to give off an unusual but effective sound which can be heard by animals. 4. Small size and light weight whistle system, easy to install. 5. Good animal alert whistle system suitable for cars, motorcycles, etc. Specification: Condition: Brand new Material: ABS Plastic Color: Black, Silver (optional) Size: Approx. 6 x 2 x 5.2cm/2.4 x 0.8 x 2.0in Weight: Approx. 30g How To Use: 1. Hold the whistle to the light and check which one is open and which is closed. The one opened is the ultrasonic whistle, the one closed is the bagpipe. 2. Please keep the surface of the installation location clean and dry before installation to ensure that the paste is firm. 3. The opened ultrasonic whistle is installed on the passenger side. The closed bagpipe is installed on the driver's side. Package list: 2 x Repeller . Note: 1. The environmental conditions for the use of a pair of whistles are that the car must be at a speed of 35 miles per hour to send out wind and ultrasonic signals, which will effectively drive away the deer and prevent further damage to your car and animals. 2. You should check the whistle occasionally to make sure that the whistle is still installed on the vehicle and there is no blockage in the hole.