[Save Your Car ] 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 at up to 35 mph speed, which will effectively steer away the , prevent any further damage to your car lost. hese will work above 35 mph.[ Easy to Install and 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.[ Safe Gift 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. Buy this warning device for your loved ones - anyone who could encounter a or a few[ Sweet 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 any blockage in the holes.