I don't know about sew-classics, but I had to take pliers to the ones I bought from April1930s. The rolled edge on the repros was a little too much for my first 301 so I had to squeeze it in slightly all the way around. I'm glad the second came with a lot of original bobbins, because I do like use my lonely original for FMQ. The fixed ones work perfectly, but I don't want to take the chance on thread breaking or anything.