The Sportline Evolution features our injection molded foam, known as one of the most durable and comfortable foams available. This foam will hold its shape for years to come ensuring your comfort for the life of the seat. Whether you drive on the street, the track, or offroad, you'll notice how the Evolution virtually eliminates body shifting, meaning your body won't get fatigued. Please note we also have a fixed back version of the Evolution available called the Evolution X. It's a bit more narrow allowing it to fit in smaller vehicles.