I think this has come up before. Easier to start a new thread.
I use a Husky workbench with long drawers for my gun stuff. I use to keep my magazines in open top trays where they stood upright.
Three things have happened:
1) My holsters didn't quite fit in the narrow drawer (2nd from bottom) and I had to move them down to the bottom. And move the magazines to a narrower drawer. Which mean now the magazines weren't going to fit standing up.
2) I got a lot more magazines and I need a better way to take them to the range than just in the bag.
3) I got a new range bag, the MidwayUSA Range Bag Backpack
So I went on a quest for plastic storage box that would fit in the Backpack and discovered the Plano 3715 fits perfectly. It is one compartment which allow me to cram as many mags as possible into it. (Dividers tend to limit the arrangment.)
So below are pictures of the drawers, old tray, the new boxes and the BackPack. Same system works with 10/22 magazines and with my 929 moon clips. For the.38spl speedloaders I lay down. These trays are just tall enough to get a tray of 9mm ammo, without the box, in there as well.
I can get 11 G17 mags in them by laying them flat and two deep. For the 929 moon clips, 22 fit just perfectly in each tray.