they do cut back on your visibility at night. I have silverstar ultra bulbs in my car and the headlight covers makes my visibility like that of the standard old fashioned halogen headlights.
I had Headlight Covers on my 08 V6 and I need to order some for my GT. They are very secure and don't pop off during a car wash or when you close the hood.
AVS Headlight Covers guard your expensive headlights from the damage of rocks and other flying debris. They're custom-designed to your exact vehicle for a perfect, aerodynamic fit and install in no time. For extra style and protection, go with Auto Ventshade Headlight Covers.