Custom fit covers will not blow off because they hug contours of car. When a hurricane comes I do tie grommets together underneath. The more layers of fabric, the cushier the cover. I stick to 3 or 4 layers. Have survived hail, hurricanes (am 100 miles inland but still get major detrius from trees) and pine cones (don't laugh -- an unopened pine cone from 100 feet packs a punch). Dirty little secret of car covers is they are "breathable", which means a micro fine layer of dust will get through. Is worst in pollen season. I just hose off cars before driving. Because I've got seven cars under cover, which need to be switched out to access rear of driveway, can't be messing with tie downs, moving blankets, or anything else that will delay quickly moving vehicles. Premium covers do cost more, but for my lifestyle, without garage, have no alternative. A cover exposed to elements year round does have limited life expectancy. Fabric becomes brittle and will tear easily after 5 or 6 years. Cover still useable, but you've got to be gentle installing and removing. Covers attract cats, especially in the winter. Can rip with their claws jumping on top of car. Are deterrents not discussable on list without igniting flame war. Personally recommend buying cover worthy of DeLo investment. Makes no sense to spend so much time, money, and energy on car then subject to cheapest cover available. Bill Robertson #5939