Grabbed some of these TSTAK modules on sale to store action figures. They're a massive step up in terms of protection, portability and aesthetics from the ratty old cardboard boxes I had them in before. Very likely overkill, but these beat having termites and disintegrating cardboard.
They're basically stackable, tough plastic shells with metal clasps and a metal rod in the lid's hinge for durability.
A common complaint I see with this TSTAK system is that the boxes have ribbing/supports/cutouts that reduce the amount of useable space inside. I completely agree that the ribbing can be a nuisance when trying to fit your reciprocating saw or drill into a box, because even just 1 inch can be a dealbreaker. But since I'm dealing with flexible action figures, the cutouts and supports translate to a negligible 2 or 3 less figure capacity.
I bought 6 different modules so I'll give quick thoughts on each.
Clear Lid, Short Box
This one looks to be the most cramped when looking at the product images, but it's actually the roomiest. The clear hinged lid doesn't have bulky support ribs to take up valuable space. The included yellow containers sit inside a giant black insert that wastes a lot of the space, but you can easily remove it all by pressing a few tabs! I dont know why this isn't pointed out by DeWalt. You can use the insert and containers to organize your car's trunk I guess.
I fit about 60 action figures in there (6 to 7 inch scale) plus random accessories.
Black Lid, Short Box
There's nothing fancy about this one, it's just a box with a hinged lid. It's the same size as Clear Lid but doesn't include the containers. Also, the lid has an extra handle and bulky ribs under it that eat up some space. I use this as a basic toolbox and it fits lots of stuff.
Long Handle, Yellow Lid, Short Box
A little less vertical capacity than the Clear Lid, but it adds it back as a separate storage space inside the lid. I use the lid storage for extra figure hands, heads, and other small accessories. The lid storage cover has ridges that when closed prevent the contents in each small compartment from getting mixed.
This box also has a long handle on top that flips down flat. I think this is intended to be used as a top box in a stack, to give easy access to the lid storage and so you can muscle the stack around with the big handle.
Long Handle, Yellow Lid, Deep Box
Same as the previous box but taller. It includes a removable tray so you can carry around wrenches or paintbrushes or whatever.
Deep Drawer
I wish these drawer modules were cheaper because they're very useful. Obviously, you can put them lower in a stack and still access the contents. If all you need is a drawer and not the stacking gimmick, just buy something else. These work great, and include a bunch of containers for organization, but the cutouts and strength-first design of the whole unit wastes a lot of space.
Tote
This is what you want if you need maximum storage with no frills. It's just a box. It doesn't even come with a lid, if you want to cover it you'll have to stack another module on top. It includes a removable insert and long flip handle.
The TSTAK Tote is about 20 bucks after tax at your local hardware store, so don't get ripped off by Amazon prices.
Also, Craftsman sells this identical system (they call it Versastack) but with red accents instead of yellow, so get whatever is cheaper or whichever color you like better.
As a final note, these boxes had some STANK on them, I had to air them out for a day. Maybe they smelled bad from being in a hot delivery truck, but it's something to consider if you plan on putting them somewhere hot.