Fits the Featherweight! Open-Toe Quarter Inch 1/4" quilt piecing attachment - scant 1/4-inch seams with precision!  Greater visibility for stitching half-square triangles (HST) and paper piecing (see photos).  If you happen to have the Graduated Throat Plate, then the 1/4" line leads your eye right to the edge of the foot for a scant 1/4" seam allowance.  Otherwise, using the right edge of the foot as you can see in the photos is what you will align your fabric seam allowance to when stitching.  Because of the openness of the foot, you have to stitch a little bit slower as you come to the end of your stitching line and the edge of the fabric, so that the feed dogs will guide the fabric straight.

This foot also works really, really well for paper piecing because you can see the stitching lines so clearly all along the stitch path.

LOW SHANK:  fits the Singer Featherweight 221, 222K and all low, vertical shank Sewing Machines (i.e. 15, 27, 28, 66, 99, 185, 127, 128, 192, 201, 206, 237, 306, 319, 320, 328, as well as many other brands besides Singer)

SNAP-ON SHANK:  fits most newer model Singer Machines as well as many other brands (i.e. Elna, Brother, etc.)