Posted By:
MEWheatAgree with Leon with one addition. I use penny sleeves, top loaders and then store both graded cards and top loaders in 7.62 mm old metal Army ammo boxes that have a rubber gasket at the top.
I am not sure if all army ammo boxes have the gasket, but they hold graded cards perfectly without allowing them to jostle around, and provide some protection from moisture/water. They make a perfect carrying case as well.