I bought a the large Sidewinder to wind Viking green bobbins because the small one will not. It winds them great and hold the bobbin nice and tight so it doesn't fly off, it even shuts off at the right load point. Problem is, in order for the thread to come off the bobbin in the right direction to actually sew with it, it has to go on the spindle upside down. (The large machine has a blue spindle which is strictly for green Viking bobbins.) When put on upside down, the little spring thingy that holds the bobbin is not quite in the right position so the bobbin doesn't sit square. This makes it wind wonky. It is very obvious that the person who designed the blue spindle never put a wound bobbin in a machine and actually SEWED with it. If the spring holder were just in a little different spot, I'd LOVE it. Or, if my machines were any other brand than Viking. I'm not an engineer, but I am very mechanical and I DO check engineers' work at work. I had to return it and get my money back. It worked great!! Just not for green Viking bobbins. :-(