We take tremendous pride in our product and our warranty. Watch out for and beware of covers with no warranty, or 90 day warranties. The warranty is by far the most important indicator of what you are buying. For example, the sub $100 covers you see online are 90 day covers at the most. Boat cover warranties are a direct reflection of how long the cover is engineered to last. The warranties on the cheap covers, if they even have warranties, are for 90 days. Some have absolutely no warranty, not even a DOA guarantee. Contrast that with our Vortex covers, which come with a solid 5 year warranty. When you pay, say $80 for a 90 day cover, you are getting a cover that is engineered to last 90 days. Our covers are engineered to last 5 years. Since there are about 20 90 day periods in 5 years, our cover is engineered to last 20 times longer than a 90 day cover. There is no comparison between our covers and the cheap covers. You get 20 times the cover for a very minimal difference in price. We can't advise you not to buy a disposable cover, as that may be what you are looking for. But, we can advise you to just think about it. Our covers are simply the best value, if you want a cover that will last, and has a solid warranty to back it up. The cover is made from 600d marine grade canvas. The fabric is then coated twice with polyurethane on the bottom or downside, UV protected, and mildew protected. It is designed to keep water out, as it is WATERPROOF. Yet, water vapor can permeate it, so it will not keep moisture in! 600d is an indirect measurement of density and weight. The higher the number, the heavier, thicker, and heavier duty the cover will be. You will see a lot of 300d, even 150d covers, which are proportionally half as thick and 1/4 as thick as our covers. Since these are waterproof, they will collect water. Use a support of some type. (We have a fantastic one!) Please contact us with any questions. We will be glad to help you.