This vintage original attachment was originally included in the Standard Set of Attachments, obtained at Singer Sewing Centers for all Singer Sewing Machines. (Yes, including the Featherweight 221 and 222.)
You will receive either the blackside or nickel-plated (silver-colored) attachment.
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)
SLANT SHANK: fits all SLANT shank Singer Sewing Machines (i.e. 301, 301A, 401, 401A, 403, 500, 503, 600 & 700 Series and all other Slant Needle Singer Models)