The S1 design moves the middle seat a few inches lower than, and back from, the aisle and window seat. It also widens the seat by about three inches. This allows your arms, shoulders, thighs, and elbows to spread just a bit more than they otherwise could, without giving the seat more legroom or reducing a plane?s seating capacity. It also features a two-level armrest design to eliminate elbow fights. The aisle and window passengers end up using the front ledge of the rest, and the middle passenger uses the rear portion.