Since it's on the intex site, I'd guess it'd be the vinyl part of the pool, and not just an overlap. To feel better, I'd call them to make sure since they don't offer free return shipping (I had to return some parts a couple years ago and it almost wasn't worth it due to cost). You could also email them. Last time I called was a few months back and their call center was closed due to covid, so I emailed and got a fairly fast response. Like I said, I can't image it being anything other than the liner that the top rails go through since it's specifically for the intex prism pool, but I'd still confirm.