Slack Thread Regulator and Tension Thread Guide, Singer (Vintage Original)

This tension unit piece (part 45863) regulates the slack produce by the take-up spring on a Singer Featherweight 221 & 222 and 301.  Check under the tutorial tab to know how to put the tension unit together, or if you are unsure about what piece you need.

If you also need the screw that attaches the slack regulator to the machine, it is available separately here.