Backrest. This is the back portion of the chassis that folds down when the X-sail is in the bag. It comes complete with a y-frame. Replacing the backrest will also involve drilling out the rivets that attach the seat fabric, and replacing the drilled out rivets when the seat is re-attached.
Please note, this part has the later model retaining pins as fitted from X-Sail #1659 onwards. It could be used on earlier X-Sails but the frame would need 2 small holes drilled. The backrest comes with the two retaining pins.
Photo is of the old style backrest with the clamps; this is just for illustrative purposes. The one you receive will have the retaining pins.