This should be a press fit.
For bigger dividers see: https://www.prusaprinters.org/prints/123422-festool-systainer-mini-4-large-insert-dividers
Shell is minimum 1,2mm thick
Part number is counting from top left to right:
1-2-3-4-5
6-7-8-9-10
11-12-13-14-15
Der Autor hat dieses Modell als seine eigene Kreation gekennzeichnet.