This foot has a smooth, flat sole with a slight indentation in front of the needle in addition to one behind. this allows the stitching of thread patterns that move forward and backward. The indentations on the bottom of the foot are not large enough to accommodate the thread build-up of a satin stitch. The center of the foot is marked with an engraved line. the slot on the #1 Foot is through the side of the foot, allowing the needle and thread to pass under the foot and the back without tangling when sewing reverse motion stitches.
The C accommodates a stitch width of up to 9 mm. There is a sensor on the foot that works with the electronics of the machine to engage the wider sttich with. The soles of the "C" feet are larger to fit the wider feed dogs of the 9 mm stitch place.