MSR IMPORTS Dog Car Seat Extender - Safer More Comfortable Back Seat Platform with Storage

Is the seat extender made of foam?

What are the dividers made of that provide the structure and support for the extender? I'm hoping this is sturdy enough for a 90 lb. dog.

I need instructions for this item, I am unable to put it together, I think missing some parts, can you help?

Does this fold down for storing?