I wasn't sure what size cover to order, so I took a chance and ordered the 27-30' for a 30 foot box. It is just a fit.The material is somewhat of a see through; it does repel water, and will tear fairly easily. The directions say to tape sharp edges, which is good advice. I put some pipe insulation on my ladder to help keep it from wearing, West Texas winds. We have installed, removed, and reinstalled the cover. The second installation went much smoother, because we folded the cover so that it was in the right location when I rolled it out on top of the trailer. All in all, without experience with other covers; I say this cover will be okay for us, and should last at least 2 or 3 years (guess).