If you have negatives, they are about 30 years old or more. Mine were kept in an envelope and when I pulled them out they were slightly bent. this makes it very difficult to load them into these shells. If yours are nice and flat, these trays are fine. If you have hundreds like me, it will take forever. Right after I received them, I found the MK1 film holder + Pro MK2 mount in the Negative store. You feed your negative through the brushes, turn the wheel and each negative appears perfectly even in the lit area, click on the image and turn the wheel to the next image. Oh, by the way, this machine costs five hundred dollars.