Fillament spool center insert 53/8 mm

This fillament spool insert with outer diameter of 53 mm provide reduction to 8 mm mounting rod. This is easy, effective and cheap to print design. This needs to be printed for each side of spool (2 times).

Second variant (V2) does save a little bit of fillament by deleting unnecessary areas.

UPDATE: New system aviable at: https://www.thingiverse.com/thing:3423076