I know your talking about travel trailers and 5er's. and their are numerous manufactures of covers for them. Each and everyone will brag to be the best and they will all offer different versions of their covers
This site provides an example of what's available, I am not saying to purchase from them because I don't know the first thing about them.
Discount Covers for Travel Trailer
They offer five different versions starting at just under $200 for one with a one year warranty to their top of the line one at just over $400 with a five year guarantee. These are all one version fits all and available in different lengths.
See how they brag about certain aspects of each version
UV protection - The level of protection is more important in the south than in the north.
Water resistance - Yes
Waterproof - is a no-no - the cover needs to breathe otherwise you get moisture buildup underneath and mold growth
Warranty- really nothing more than a marketing ploy-Try and prove it was due to a manufactures defect.
Trailers and 5er's are pretty much standard in width and height when in storage/transport mode, although they do vary in length. The cover manufactures know that so they offer a variety of stock sizes that will fit different RV manufacturers. Finding a cover to fit your particular RV should not be a problem.
Do an internet search and then read reviews, look for U tube videos, etc. You don't really need to concern yourself when doing research on a brand cover as to whether a person is talking about your specific RV or not because that company will be building the cover with the same materials and using the same techniques regardless of the size or manufacturer.
I was given a hand me down 1998 Forest River Wildwood 5er about six years ago once my father got too old to enjoy it anymore. We would cover it with either a silver or blue plastic tarp. They did the job, were cheap, and disposable. Cleanup in the spring and markings on the aluminum siding was another story. Since the trailer was already old and weathered, I didn't see the need for a fancy cover.
Custom made covers are also available but expect the starting price to be just under $1000 for one that will cover a 26 footer.
Now that I have spent $85K on a MBS Sunseeker, I have decided to purchase a real cover and that My requirements are for a cover that will last, not damage the paint, not cause moisture buildup underneath it, and provide adequate protection from the elements and Michigan winters.
We ordered our Sunseeker with a Trekker cap instead of the Stock overhang type cap that contains a double cab over bed. This being the case, I have been unable to find a "one size fits All" cover and therefore have decided on the custom built route.
During my research along with the responses and material samples I have received, I have pretty much decided on ordering a custom made cover from CalMark Cover Company, RV Covers 6 YEAR warranty, rv cover, trailer cover, 5th wheel cover, toy hauler covers. CalMark RV Cover Co - Sunbrella RV Cover
, It will be a reinforced water resistant cloth cover that will be custom fit for the vehicle. They have been in the protective cover business since 1982 and their covers are built with properly sized zipper coach doors that are located in the proper place,
I can't give you the price at this time because Murelene and I haven't had a chance to input the 14 measurements they request as well as 2 more I will add because of the Trekker cap along with the additional information about AC units, ladders, awning, etc. They have a specific measurement sheet for each RV type.
If you are interested in a truly custom cover, check them out.