From the announcement:
These are the new shipping containers, they replace the 2 older versions (if you want the older ones just let me know during the survey)
I am very proud of these, they stack very nicely thanks to the top rails and indents on the bottom of the containers. also the side rails are there to support future walkways and other things coming down the pike.. these are already the blank option so you only get 2 per slot option
These are also the reward for every one delta and above at the 16K mark by the way.