Would have helped if photo showed correct application
Singer Featherweight 221 Spool Pin Spring.
Singer Spool Pin Spring 45826 Fits Singer Featherweight Model 221.
When this Spool Spring tool is used with the Spool Pin Red Diskit reduces noise and thread spool movement on spool cover while sewing. It works well with certain thread brands like Mettler and Guterman. Auriful thread cone is also notoriously large centered internal diameter works miracles in reducing the space making the sound of sewing much less.