Large area, great flexibility, best quality.The Back F consists of 6 felt squares and 6 felt rectangles in a sturdy wooden frame, which is made to match the inserts.The advantage over the sliding cushions: You can also do larger bobbin laces on it and always bring the working point into a position that is comfortable for you.By inserting smaller inserts (502124) the pillow becomes even more flexible. All felt inserts for the sliding cushions can be inserted into the Back F.