The seat in my folding manual wheelchair was sagging badly after about a year and it made my back ache. This no sag cushion is just perfect. It has filled the sag and my wheelchair is now comfortable again. I sit in this chair for most of the day so the relief is much appreciated. Also its fits my 16" chair as well as the larger 18" chair. I am very pleased with it. The seat cover is a nice soft plush type fabric and there are hook and loop straps to hole the cushion in place.