This is a gridfinity 4x3 drill assorted bit holder - there is no specific slot for specific size, you just pile the drill bit in and sorta arrange them by size. 

There are spines at the bottom of box to keep the drill bit from rolling around too much when you open drawer, but it can't deal with much more movement than that.  They are also just a suggestion.. You can throw them in anyway you like and it won't disagree with you. 

Stackable.