The accessory case is made from polypropylene. It is a strong and durable but flexible plastic which wears and resists breakage well.
The case has configurable compartments and can hold a large number of accessories. The size of the accessories would affect the quantity count of course.
The accessory storage case WA4227 is included in every MAKERX combo kit and the WX739L. The tool only kits do not include this case.
No, there is no way to lock the case, but there is a latch that will hold the lid closed until someone releases it.
There are moveable dividers inside the case that allow the compartment sizes to be changed.