Nurge screwless embroidery hoops are made of superior quality, hard beech wood ~ fine sanded and hand polished for a super smooth natural wood finish. The quoted metric sizes (mm) refer to the outside diameter of the inner hoop. Screwless continuous hoops are ideal for displaying your embroidery, cross-stitch or needlepoint creations after you have finished them. They can be flat wall-mounted or added or used as a picture frame. The gap between the hoops allows for a stabilizer or thicker fabric. If too loose, the inner hoop can be bound with twill tape or bias binding to make the fit tighter.