This is the evolution of the toothpaste tube roller. Modern plastic toothpaste are not ideal, they suck (in air after use). This means you can't readily tell when they are running out and causes the occasional pneumatic spurt of a glob of toothpaste. 

Attempting to use a simple one part tube roller results in it springing back out straight which is a bit rubbish. This model captivates that unruly tube in the attached 20mm cylinder, keeping things neat and tidy.
 

The cylinder requires a good strong push on to the end of the slotted part to assemble, this is intentional so that things are not flopping about. Also note, that for a clean print, on bed only tree supports are set in the profile for the push fit tangs on the tip of the slotted part. 

As this is an evolution there are earlier models which may suit your application better (and print quicker):

• For aluminium tubes see: [https://makerworld.com/en/models/1064717-tube-roller-key-no-more-squeezing-from-the-middle](https://makerworld.com/en/models/1064717-tube-roller-key-no-more-squeezing-from-the-middle)
• A version without the tube see: [https://makerworld.com/en/models/1156301-toothpaste-tube-roller](https://makerworld.com/en/models/1156301-toothpaste-tube-roller)