Is this the same as what's in the wilton books (the plates and push in legs) or is it something different?
If it's different do they make square plates for it? Are they really sturdy enough to transport the cake stacked?
The SPS seems to be available in several configurations from more than one company:
Some of the SPS systems have "locking" plates which would make them very sturdy.
Here's an illustrated guide to the different SPS systems:
I believe I also came across locking square plates.
Thanks JanH! Where can I find the squares?