Thumb Screw for Presser Foot and Attachments -- fits all Singer Sewing Machine models, including the Singer Featherweight 221 and 222K, as well as the Singer 301 (301A). This is the screw you need for the Seam Guide as well.
The photo shows two screws so you can see the threads as well as the head of the thumbscrew for comparability. However, this item is for only one screw. A quantity of 1 = only (1) screw.