I would not recommend this item
I can sit on it for just a few minutes and it goes flat and gets really hard.  It goes back to its original state after a few minutes when I get up but is not much of a cushion.  I only weigh 110 so its not from the weight.  It is also really big.  I bought it to use in my car but its way to large, it hangs over the seat and covers the seat belt hooks completely so I can't use it.  I would not recommend this item.
Rating: 1 stars