No expert here but something I noticed or assume. I will use 21mm casing as an example. To get the collegian casing on as packaged it is recommended to use 13mm tube. But, if you unravel the casing you can use a 19mm (3/4 inch) tube instead of the 13mm or 1/2". To me it would be much easier to push with larger tube even though you will have to make shorter runs of your stuffed meat with the same hank.