The three sizes; universal, semi-custom, and custom are available for virtually all the covers on the market. Once the material, and hence the type of protection, has been selected, one can choose the size.
Universal covers will fit each and every car, no matter what size it is. Vans come as a separate size, but aside from that, big or small, the universal cover will fit the car. This, as with everything has its advantages as well as disadvantages. The big advantages with universal is that as it will fit any car, it can be lent out to family and friends. Also there is no need to update the cover, with the purchase of a new car. Universal covers are therefore very economical, even more so considering they are not expensive in the least.
However, a universal cover will not fit any car perfectly. Either it will be too big, and look very baggy, with loads of excess material flapping about wildly. Or the car will just about fit, leaving a few things peaking out and uncovered. Therefore, it is said that universal covers do not provide a high level of protection. It will certainly do its job well, and for some this may be enough, but the protection will not be of a high standard.
By contrast, the custom cover is tailor-made for each car. The owners select the colour and design of the material, and even have the option of putting a logo on the bonnet. The cover is then made to fit that particular car exactly, taking into account mirrors and aerials, and making pockets for them. Naturally this give the car a far better impression than the universal cover. The car looks very smart and chic, as well as much more upper-class, when covered with a custom.
The protection a custom provides is graded the highest as it will cover every inch of the car perfectly. There would be no room for anything to find their way in, as the cover is snug against the car. The disadvantage of a custom is the price. It is relatively expensive to buy a custom, and will only fit that one car. However if owners have just bought a new car, and are hoping it will last, then it may very well be worthwhile to spend that bit more, and help the car survive for longer.
Semi-custom covers are often termed 'the happy medium'. The cover is made to fit a selection of cars of similar shape and size. The fit is therefore better than the universal, and doesn't work out as pricey as the custom. The protection provide is extremely good, as the cover will fit the car almost exactly. Admittedly the custom will provide better protection, and look better, but the semi-custom, works out a lot cheaper, and will do the job almost just as well.