I first separated them into groups depending on location of the zero line: right at the top of the plunger, above the top, below the top. Just by simple visual inspection. It doesn't have to be perfect, just in the right area. I may have small variation, but I just couldn't see the calipers well enough to use them.You said you checked all your syringes. Are you using calipers to do that? I tried & it seems impossible to do just looking at them? I'm going cross eyed!![]()