Although a couple reviews on their inability to stack concerned me, I couldn't pass up the low price. I was pleasantly surprised that infact they are designed to stack, quite well actually. There must have been a design change.
Our team was using this to hold camera gear outside in the elements. The manufacturer changed the release valve to a Gortex/EPTFE style vent (great idea!) except for THIS particular box they didn't put in a Gortex vent. Water poured (and I mean poured!) into the box and destroyed an expensive mirrorless camera.
If you've already bought one or if you're considering buying one be sure to test the vent. It might be a straight hole into the box.