Assuming this is a “total vehicle” cover, and not just windscreen covers? (Windscreen covers have been well discussed on here – search).
I’m possibly not the best person to comment on “total covers” because I don’t like the idea of them and I really don’t see the need for them. I know people cover caravans occasionally.
My prejudices come under two headings…
The need for a cover – Our Exsis’ are based on commercial vehicle chassis’, where the greater damage from the elements is on the underside, the chassis. The bodywork is protected by enamel/fibreglass/plastic which, if kept polished and the rubbers silicon’d, should happily weather a winter without any damage except dirt/leaves. Just make sure it’s well polished before lay-up.
What a cover will do – Yes, a cover will keep the dratted high roof clean of dirt and leaves, but it will billow to some extent, damp wind WILL blow around under the cover. It will flap somewhat and therefore rub the sides and roof, and although the backing is soft with the material breathable, rubbing and wear spots are a possibility. I cannot see the need for what is a VERY expensive item, difficult (because of the height) to put on and take off, and all just to keep a bit of dirt off the polished finish – rainwater does no harm. A jet wash in March would clean that, followed by a polish and Hey Presto!
They offer no extra “security”, as I’ve seen advertised. A Stanley knife would soon give access to door lock/window, where a thief could then operate “under cover”, so to speak!
So… that’s my prejudices! No, I’m not a fan of them but if you still desire to fit one, I would just recommend getting the best you can afford – a cheap one will surely disappoint.