From the designer:

This is a custom insert that I have designed to fit your Milwaukee Packout to store all your 150mm/6 Inch Orbital Sanding Pads. It specifically fits the Milwaukee 48-22-8424 PACKOUT Toolbox.
LINK: https://www.milwaukeetool.com/Products/Storage-Solutions/PACKOUT/PACKOUT-Tool-Boxes/48-22-8424

Comes with two sets of custom files! Simply pick the option that best suits you:

File Set 001 - Festool - The specific tool this is designed for is the Festool ETS EC150 Orbital sander: https://www.festoolusa.com/products/surface-preparation/random-orbital-sander/576339---ets-ec1505-eq-plus-us

File Set 002 - Generic Sanders - The Festool specific sections have been removed allowing you to store other brands of 150mm Orbital Sanders. Due to the large variety of designs/shapes available for 150mm Orbital sanders, I cannot make any guarantees whether your sander will fit. I did however want to ensure the option was available. If it can fit in the toolbox upright, there's a chance it will be suitable.

Features

• Efficient Storage - Store and sort your 150mm orbital sanding pads like never before! 4 dedicated spots are available for all your storage needs. Additional tub storage is available surrounding the 4 slots for your smaller items.

• Grit Sorting - I've designed a fully custom system to label and sort your different grits of sandpaper. This allows you to store multiple different grits in a single slot! The divider consists of a disc that sits between the pads which has a handle attached. This handle allows for easily lifting out your chosen sandpaper. 

• Grit Labels - I designed fully modular printable labels that slot into the dividers handle section. You can see these above as they are printed in red for the photos. Pre-made STL label files are included for 40, 60, 80, 100, 120, 150, 180, 220, 240 and 400 Grit sandpaper.