Large, heavy, for its purpose.
I tried this in my computer chair my car seat, my reading chair.  I have back and hip pain particularly when sitting "straight" up for more that 15-20 minutes.  Simply did NOT work in the car seat at all.  Nor in the computer chair, although better than in the car.  A little bit in the reading chair but truth told its not worth the money.
Rating: 3 stars