They are actually wind deflectors that are there to cause a downward wind pressure on the trailing edge of the bra so that it doesn't slap up and down on the hood and damage the paint. Learned this back in the '70's when hood bras first started showing up. If it starts to rain, get the bra off! Moisture traps under the material and will cause blistering of the finish.

 

I don't think i'm going to go threw the hassles of taking it on and off. i had one on my sunfire for 2 years and it never gave me any problems, had little scratches on the paint but no biggy to me.theres aleady rock chips there anyway, so it works good for covering them