This is a custom insert designed by Jonah Pope Design to fit your Milwaukee Packout and store your M18 Multi-tool and accompanying kit. It specifically fits the Milwaukee 48228435 PACKOUT Compact Organiser.
The specific M18 Multi-tool that this is designed for is model M18BMT-0 as below: https://www.milwaukeetool.com.au/discontinued-products/M18BMT-0.html