I store two 4 1/2" grinders in a Midi III; one with a metal cutting blade and one with a diamond blade (we install commercial steel doors and do commercial locksmithing and access control work among other things). The grinders would fit into a II, however, in the past I kept them in Plano tool boxes with accessories in a tray. By trimming the ends of the tray I could also fit that into a III. I use Midis for my 4 1/2" Hitachi jointer, my Milwaukee band saw (the new compact), My metal forming tools, my 18V Milwaukee system tools and my Flex and Makita die grinders. By switching from Planos to Systainers my tools no longer slide all over the back of my van. LOVE FESTOOL!