travelmate extra-large memory foam seat cushion – perfect for office chair and wheelchair – does not slip even on smooth marble floors – washable & breathable cover – relieves back pain – 19”x17”x3” travelmate new! this extra-large seat cushion is constructed of a highly resilient, furniture-graded foam with a layer of high density memory foam on top. this unique design combines the two key elements you are looking for: comfort and durability. its extra size enables it to provide bigger coverage to dissipate pressure more effectively while conforming to body contours. it is firm enough to give you good support but not to the point of being 'too hard' to undermine its use as a cushion. it can be used in the car, home, or office. it is designed to help relieve back pain, numb buttocks, and other discomfort associated with prolonged sitting. what you get is a high quality product for a lot less than what you have to pay at specialty stores.