The seat cushion is very well constructed and more firm than the less expensive cheaper seat cushions found online (Google, Amazon, etc) and does not fully compress with heavy person as almost all of them do. However is is advertised (at least on Amazon) for people with weight up to 500lbs and it is only 3 inches thick. The thickness and amount of padding/cushion is simply not adequate for someone 400-425lbs or more—it just isnt thick enough in my opinion especially along its edges which compress enough to allow pressure to develop in a short time along the backs of the thighs at edge of the cushion, especially if the cushion is being used on a firm seat with a hard or firm edge. Although it is offered in multiple lengths and widths, the 3 inch thickness is the only option for all of them. It might be vastly improved and acceptable in a 4 or 4 1/2 inch thickness or with an asymmetrical increased thickness along the leading edge where thighs will cross it. Otherwise in its current configuration (at least for someone 400lbs or greater) it becomes rapidly uncomfortable after sitting on it for 15-20min necessitating standing up for awhile to relieve the pressure on back of thighs.