Cari, thank you for the information. The Kenmore is a series 158 machine. The Singer 237 uses the removable metal bobbin case that fits in under the machine so that would use the class 15's and the singer 347 has a drop in bobbin so then it would use the class 66 bobbins, per you information. The Kenmore metal bobbins are straight sided and they fit in the Singer 237 bobbin case so I will try those in it. Have to see if I can find the bobbins for the 347, I am sure I have some around here somewhere. Thank you again for the information!