[hirosh]

i'm with bill, the good ones may be expensive, but they're worth it. i got a covercraft one (forgot which one) after seeing the difference in the rain between the covercraft one and a cheap one.
the covercraft one, the water was beading and rolling off, and kept the car relatively dry.
the cheap cover was like a surface that hasn't been waxed for years, the water would just puddle on the surface, soaked through the fabric, and got the car wet.