It's not a grab rail. It's a seat basket. Mine is so sturdy I use it to walk the bike around all the time. They are really for solo bikes though. Most adult back seaters would not appreciate the loss of space in their
crotchal areas.
Not mine.

It does make taking the shocks off a bit more work (tire changes).
I don't think it would go on behind an Ultimate King, if you had one.