Is this a single layer cover? Or is it a multi layer like the Evolution covers? I have a paper cover that's similar in appearance to yours. It is used exclusively outdoors but not consistently. It doesn't fully filter water, but it does a good job in protecting the car from heat and UV. Its deterioration comes from folding the cover.
Same with the Tyvek covers. They are quite water and tear resistant, but constant removal and folding for storage tends to start small cracks that eventually lead to water and dirt passing through to the car's finish. I do like the Tyvek covers best of the two. The paper covers will eventually start to leave fine paper powder on the car when removed. The Tyvek covers have a soft underside that doesn't damage the finish and allows the cover to slide on the finish rather than sticking. White ones really keep the car cool inside, even in mid-90 degrees. The ideal, I suppose, would be to put the Tyvek cover on the car then cover that with the paper one.
The Evolution covers are made for the specific car and the one for the Fiero can be ordered for a notchback or fastback, either with or without spoiler. Mirror pockets are form fitting.
My endorsement of the Evolution covers isn't totally because I own stock in the company. I have seen them, have had friends who had them, and I know their protective abilities. But they're a little pricey compared to some other covers.
