Product description 1.Save Life: The two pair of whistles for car include 2 ultrasonic whistle and 2 wind whistle. A pair of whistles emit wind and ultrasonic signals in a collaborative environment over 35 mph speed, which will effectively steer away them, prevent the further damage to your car lost. These will work above 35 mph. 2.Easy to Install & Removable: The bottom of the whistle is the strong adhesive strips , allow to mount on the front bumper or roof of a vehicle which with good airflow. It would not fall off even driving when raining or snowing. You can also screw the bases down with two small screws. they can be removed from their base for cleaning or going through car washes. 3.Safe Alert for Driver: That is a defensive car accessories for driver who live in a wild area. The whistle produce ultrasonic frequencies and wind sound warn, thereby reducing -vehicle collisions. 4.Instructions: Please check and clean air-activated whistles periodically to ensure that the holes do not become blocked/clogged by debris. You should examine the whistle occasionally to be sure it is still mounted to the vehicle and does not have other blockage in the holes. 5.What You Get: 4 Pcs Deer Whistles For Car. The ultrasonic of the deer whistles are only audible to wildlife at high speed. The sound don't affect humans or pets inside your car, as it is way out the normal hearing range of people. Every vehicle need one pair of deer whistles.