I don't know why a Singer 301 tension would be much different than a Singer 401. The insides will be the same if nothing else. I put the stud from a Touch "n Sew tension on a Singer 327 this afternoon - the one on the 327 was bent - well pretzel-ed.... I put the spring from the T&S tension on the Singer 301 and I sent the little part to Judith already. That will make 3 machines that T&S has saved just from it's tension!!! Hurray for parts machines. Oh and there are still good parts with the old tension!!!