Upgrade Design: These deer whistles have been improved, comparing with the single hole whistles. Two holes can expand the range of the voice, which can keep the animals out of the road more effective.Function: These safety alert devices make use of the wind to produce the ultrasonic wave which is harmless to animals but can drive the animals out of your car for 1/4 miles, safe for your drive and animals.High Quality: These deer whistles are made of premium ABS plastic material which is tough, reusable and durable. It can resist any kinds of severe weather, and the tape is waterproof, it will not miss easily.Easy to Install: Each warning whistle is attached to self-adhesive tape, you just need to remove the paper and stick the whistle on the car. Please make sure that the side with 2 holes faces to outwards.Package Includes: This deer whistle set includes 6 pieces of deer alarm whistles, 2 are transparent, 4 are black. Two kinds of colors can fulfill your different preferences and your needs to match your car.