Strong Case lower drawer removal

Hi All... Are the four fasteners that holds the bottom drawer on to  the main box hex head? I've tried every size and they're either too big or too small. I'm looking for Goldilocks... Just right. What am I missing here? 

Tia!

Rivets?

There is a quick release on each drawer to slide them all the way out. But mechanism is riveted in place on mine. However, if your talking about the whole extra drawer you can purchase (like picture below) then it is anybody's guess. Mine did not come with the 1608 attached. I had to drill and place my own screws. I used phillips head sheet metal screws.

I really need to get a new phone. This camera sucks.