There is a line that Carefree sells that is super cheap for the OEM. You cannot buy this model or even get parts for it. The tube is so small that it bends when the slide goes out and the material is super thin. It sags terribly and rain puddles until it collapses.
For two S/O's, I paid $450 for this junk model which was about half price.
It wasn't worth it. I would have rather paid twice as much and installed Carefree's cheapest model myself. It's way better quality than this OEM Carefree model.
This is what the cheapo looks like. I would not buy it for any price or even take it for free. Someday I'll have to replace them and deal with all the holes left by these junkers.

Don't get me wrong, a topper is well worth having when camping under trees or to keep the sun off the roof of the slide.
But these aren't worth having.
Oh and yes, they stretch a lot.