That type of feet (top clamp) come in many variations, so you have to get the correct one for the machine. Usually it's manufacturer specific, not model specific. Ones for a White won't fit a Standard or National, though they look very similar. Either test fitting or measuring is the only good way to tell exactly what they fit.
These four are not interchangeable between manufactures. They are Standard, National, New Home (older) and White.
The feet are almost always interchangeable between rotary and VS machines of that manufacturer. The shirr plate and underbraider are not, so if you see a set marked "Rotary" it's because of these items, not the feet.
The earlier Standard is a slimmer machine, and takes a bobbin case that has a solid pin. The spider (the half round item above the bobbins ) also has the solid pin. That, along with the needle plate to the right convert the machine to chain stitch.
The later model is not as thin (refered to as Stout) and takes a bobbin case with a hollow center, and the spider also has a hollow center. That machine takes a larger needle plate too.
Standard "slim" version
Standard "stout" version (later model)
And the two bobbin cases - stout on the left, slim on the right. Though the bobbins look different, they are interchangeable, and tests have shown a Singer class 15 bobbin will also work.
