Stop wasting what you buy ! These three plastic tube squeezers (one of medium tubes, one for small tubes, one for bigger tubes) will reduce the trash that you produce and save you money.
They are meant to be slightly hard to put on, but are designed to be easily removable and reused.
Insert the side with the largest opening from the bottom and push it up !
(Not designed for aluminum tubes.)
Make sure to rotate the parts so that the slot is facing up before printing (+90 degrees on X).