When you but the embroidery thread label look and you will see a three or five on the label. That is the size thread meaning in thickness. Three is really thick and I have used that only once to make a doily. I used size 10 up to size 30 thread but after that I find it is like sewing thread. I even tried using sewing thread with three different colors as I have seen doilies using it. Way to much for me right now. I prefer seeing my thread and not trying to do it with a magnify glass. I know people who do use one but my eyes are good!