I do not know what the inside diameter is, but....if the film chamber is big enough, and you hold the loader upright, so the weight of the bulk roll is resting on the center spindle, and the bottom of the full spool of film does not touch the bottom wall of the loader then you should get no scratches. You can determine all this from touch in total darkness, so as to not spoil your film. If the full spool (core) of film does touch the bottom of the loader, then remove the film and put it in your paper safe or back into the can it came in, and build up the center spindle of the loader with a little duct tape. It may be a little trial and error, but it will work just fine.