Are you talking about the little tool you pull strips through and iron? I use the biggest one the most so I can fold it again in half to make a double fold bias tape.
This was on a list of things you should not ever buy. So I never have. I just cut my fabric and use the bias foot with my machine.Another item was the bobbin winder. Saved my money..
i don't use bias there i use my foot on my sewing machine that rolls it and turns it up all in one,i forgot the name but i call it an edge hemmer??hugs
Was hoping for some comments. I have been considering buying one too. Hugs, Susan