From the designer:

This is a custom insert that I have designed to fit your Milwaukee Packout to store your M18 Impact Driver (Gen 3) and accompanying kit. It specifically fits the Milwaukee 48228435 PACKOUT Compact Organiser.

The specific M18 Impact that this is designed for is model M18FID2-0, link is provide here: https://www.milwaukeetool.com.au/power-tools/impacts-and-fastening/impact-drivers/M18FID2-0.html

BELT HOOK NOTE - PLEASE READ

Please note that the Impact Driver won't fit in the Packout with the Belt Hook attached. It is physically too tall for the Packout internals even without the insert.

We now offer latches to identify which tool is in which case.  Latches are offered at a discount if purchased with a matching insert and are sold by the pair.