The secret to the extraordinary comfort of this cushion is the valve. It lets you customize the seat to your specific comfort level. ROHO Shape Fitting Technology makes the difference. The LTV Seat Cushion (18"W x 16"D) is made of individual, interconnected air cells that allow air to slowly transfer from chamber to chamber and evenly distribute body weight pressure. Weighing only one (1) pound, the LTV Seat Cushion is lightweight and easy to fold.