Measures 13 inches wide and 10 inches deep. Generally used with the XL Seat Back. The notched cushions replace the standard bench seat cushion. A 3 inch notch allows either seat to be positioned closer to the front of the bike. If notched seat is moved all the way forward around the front frame, tryke cannot use Rear Steering. You can still use a Push Bar. Cannot be used with a Separator Cube.