This is the back of the cover, the piece that turns a finished embroidery into a real cushion: the grey cotton etamine already has the zipper sewn in, so you simply place it right sides together with your stitched front, sew the four sides and turn the work through the zip opening.
The zipper lets you take the pad out whenever the cover needs washing. The cushion pad and the embroidered front are not included: the back fits Vervaco front cushions and any other piece of the same size, worked in cross stitch or half cross stitch. If your embroidery is smaller than the back, add a fabric border to bring the two panels to the same size.