I've always been confused by needles also. Why are there so many different sizes???? For my viking designer, I use Schmetz universal 130/705 for piecing (for no reason; I just guessed), found I needed a top stitch needle for thick thread and bought 130N and for some reason decided I needed quilting needles and bought 130/705 also. All this was a shot in the dark. What SHOULD I be buying? They're also so expensive!