These are actually very sturdy, which is great! 

It was a bit of a challenge getting the top set of bolts in with the lip of the planter, but I was able to do it using a pliers to hold the nut. 
There are four bars that go across the middle section to help the planter hold it's shape. 

I bought two identical ones and did some light modifications to have one, long, 12ft by 3ft bed. I divided up the cross bar supports. It was pretty easy to make the modification.

Overall, I am really happy with these and would recommend!