I've got a set for each Singer - and some "extras" taht are unique. I've got all four styles of 66 Back Clamp sets, though I've only got two machines.
Then I went to Greist so I could get a set for my New Queen and Two Spool . . . and then I had to work on collecting one for each of the 8 Needlbar lists . . .
And THEN - I went overboard after I found a few oddball sets - and now I'm collection Johnston sets from the late 1880's. From what I've read - Greist bought out Johnston. . . I've actually found on Ruffler that looks just like the funny one for the 66 set (the one that says "66" on it).
But back to the OP - what Singer do you have? Is it short or slant shank? I've got a lot of short shank feet, but no extra long shank (DH took my extra 301 set to sell with the 301 he just fixed up).