Shot in the dark

I have a Weber grill cover. I am hoping to sell it on CL and would like to know what grills it might fit. There is no part # that I can find on it. There was a label, like a shirt label sewn into the inside seam and it had a "28" on it, but I figure that is just the employee number that made it or QC'ed it. Does Weber make a different cover for each grill model/year or are they basically one size fits all?
Thanks, and I love this board. Lots of great members and lots of great knowledge.

Weber has dozens of different covers, some are more generic than others and may fit numerous grills and some such as a performer cover or WSM cover are specific to that grill.

Hmmmm, I have a couple Genesis three burners and a couple Spirit 2 burners. I guess I can just try it out on them and get an idea what grills that it may fit. Thanks.