I use the 1/4" foot with the metal edge that came with the "Quilter's Companion Set" of my Janome. I've never actually measured to see if it's absolutely accurate but, in my experience, if you carefully use the same foot in all the piecing of your top it will fit together at the intersecting seams and the points. If I took part in a round robin quilt I expect I would have to be more precise but so far I never have. As I only quilt for pleasure I don't want any extra hassle. The 1/4" foot (with edge) is fine for me.