The crown serger features a 3/4 lay-in thread system with lower looper threader.stitch options include 4 thread overlock, 3 thread overlock, narrow hem, rolled hem and ribbon lock stitches.the machine has a free arm/flat bed convertible sewing surface.the crown serging machine also offers a lower looper threading system for easy thread changing.the differential feed improves sewing results on stretch or thin fabrics to give you a perfect finish.