I suggest looking at covers from Cabelas (now combined with BassPro). I have been using 600 denier polyester covers. The 600 is very important - anything less is not worth it and will not last anywhere as long. I have been using one on a basic Grumman 14' aluminum semi-vee for several years now and it still looks new. It fits well and importantly breathes very well. At the beginning of each Spring season I use at least two cans of spray silicone which keeps the cover very dry. If it is a very rainy season I sometimes spray some more to keep things dry. I do not trailer with cover since I live very close to a local lake. I have tried a number of covers over the 24 years I have owned the boat and this is the best cover by far. For longevity only use the 600 denier material which far outlasts the thinner 300 and 150 denier covers. These covers last me at least 5 seasons or longer.