I struggle with lower back pain and sitting and sleeping, and had high hopes for this cushion. The large size seemed ideal for my large work desk chair. Apparently made for wheelchairs, I expected it to last long, though it is not refined in design but has a more industrial feel to the design. The first month or so it performed well. After just one month, it began to sag in the middle rear, and after another month, it us unusable and has caused me more back pain than just using a folded blanket. Typically when things like this sag I try to flip them around or over to the other side, however as other reviewers have said it feels like sitting on rocks on the other side. Too bad.We ordered and paid for the large (18"x18") version of this cushion for my wife to use on her DMI shower bench; however, we actually received the small (16"x!8") size (see photo of the tag) which is a little cheaper. We did not send it back because it fits the bench very well and she needed it right away. She is using it without the cover and it performs as advertised. It would be nice to get a credit for the difference in price though.the cushion worked very good and its water resistance. I can use it in the bathtub.This seat is perfect! Not too soft but firm. Is good for sitting for a long period. Made getting out of chair much easier. I have several other cushions but this one is perfect.Does not help it hurts and no returns that's terrible.Very comfortableWas just exactly what I was looking forCushion is comfortable, helped relieve back pain. Being portable is a big plus also.