This attachment converts low shank machines so that they can take snap on presser feet.
Snap-on feet are now the most common feet available, and are generally more affordable and available in a wider variety of styles.
The black plastic release button is easy on your finger (the shanks with a metal release button can be harsh on your finger, especially if you change presser feet frequently).
Simply screw the attachment onto the shank of your machine.
Will fit most low shank machines.