They can be molded onto the hood like the pic's above. I'm one of the three with them on my car, but they're not molded on. I think they look okay though. They still keep things cool. And FYI, the vents he is using are the exact same kind I (we?) have.
Linky Poo's:
Close Up -the paint matches better than it appears in this pic.
Underside -hadn't washed it yet this day
My car -pic. taken Saturday
