My parsons chairs are wider in the seat then most as the slip cover seat seams come far short of the edges.
However, I don’t think this the manufacturing problem. It’s just my chairs are wider. The back and top fit just fine.
But because the fabric is having to cover a larger seat, it makes the whole cover shorter. So it doesn’t cover about 3” of the original bottom skirting. 

I will make my own in the near future but for now, it’s ok.
The fabric is good. It’s got a herringbone weave, and mine are the “natural “ but are a creamy tone. Again, ok.

For the price, these are great!