Instruction: Output yes if the supporting document can answer the given question. Otherwise, output no.

Input:
Question: is back adjustable up/down  thanks
Document: This seat is extra large with back rest. Gives good support to both buttocks and back depending on the stance while riding.
very comfortable for us with little natural rear end padding,  The only shortcoming (minor) is that the backrest is so far back it interferes with opening the cargo basket on trike.
Also, the material is nice looking and tough, but slippery as well. I'm tempted to put anti-slip tape on key areas of the seat: A Hassle. However, decent support, for someone with back issues big time.
Got this seat for an electric scooter. Finally bought the scooter, mounted the seat, but found out that the seat tips backward when I leaned against it. Tightened the seat bracket tight as I could get, it still tipped back in mid-ride. Finally had a bike shop weld the seat in one position -- a harsh remedy, but otherwise the seat was useless.
Love it!
Answer: no