From the designer:

This is a custom insert that I have designed to fit your Milwaukee Packout to store your M12 Installation Driver and accompanying kit. It specifically fits the Milwaukee 48228435 PACKOUT Compact Organiser.

This design actually includes 2 inserts help you maximise your set up! Once the Drill is accounted for, there was still extra space left which is why I designed an organiser tray to sit underneath the M12 insert. This extra insert is perfect for storing your driver bits, drill bits, screws and other items to go with your M12 Install Drill!