Deer Whistles Wildlife Animal Repelling Alert Warning Whistle Car Repeller I have here a 2 piece deer alert whistle set. Works on your auto, truck or motorcycle, these whistles alert animals up to 1/4 mile away from your vehicle. Begins working at 35 mph. Now, a deer alert whistle is just that... it alerts the deer of you coming down the road. It does not repel. I only say this because some reviews of this product, and this goes for any brand, have said, "didn't repel the deer, they just stood there". That is exactly what it is supposed to do. I put repelling in my title because it is a searchable word people use. 1-1/4 inch by 3/4 inch air scoop. 1-1/2 inch by 3/4 inch mounting tape on bottom. Easy to install and comes with a debris clean out key. Installation instructions are on the back of the package. See photos. Always install right side up. Thanks for stopping. Please visit my slow growing store, read about me, my policies and view other items that may be of interest. **I always have money saving volume discounts on most items** David - thediscountretailer