4/0: A printed piece with full color printing on the front. 4/1: A printed piece with full color printing on the front and black printing on the back. 4/4: A printed piece with full color printing on both sides. Insert: The printed piece that goes in the front cover of a jewelcase. Traycard: The printed piece that goes behind the disc in a jewelcase. Panels: The total number of squares that make up a printed piece. A basic CD insert has 2 panels (one square panel on the outside and one on the inside). A basic folded insert has 4 panels (2 on the outside and 2 on the inside).