First, this is actually three individual sets of chair cushions, not a sofa cushion. When I put them on the sofa, they look like they are chair cushions trying to be a sofa cushion. They are not attached to each other, nor do they have straps or ties to hold them in place on the sofa frame.  The material is slick enough that they slide and pop up. If you have one of the bigger boxier type sofas, they may work well for you.  I'm going to have to work on these and maybe I can  attach tie-downs or something.  I bought two of the same size sets for my chairs at Lowes on clearance for 29.99, that are at least as good if not better quality.  If I can figure out how, I'll post a picture.