The "A" in this Buttonhole Foot stands for automatic sewing of the buttonhole. You can use this foot on Bernina machines that have a maximum stitch width of 5.5mm and a variable buttonhole length of up to 30mm. You can sew buttonholes with or without cording. The sensor can measure the buttonholes automatically based on the size of the desired button. This allows you to produce any number of buttonholes of the exact same length. Use together with the fabric-feeding aid or the buttonhole leveler as well as the buttonhole cutter and button-sew-on foot to create perfect buttonholes with consummate ease.