You need at least the medium Orbit <14" diameter> to around a 10" Jolly, and a large Orbit <18" diameter> to go around the 14" Jolly.
All my Jollys are 10" .. and all my Orbits are Medium <14">, but I had two Orbits done with 1/2" rope instead of the standard 3/4" rope .. one of my Quakers is a bit handicapped, so he needs a narrow diameter in order to grip things.
In my pics below, the first pic is a 10" Jolly with a medium 3/4" Orbit, but I turn it on it's side .. lol .. the Caiques like it better that way .. don't ask.
The second pics show a sad, but effective homemade Orbit around a 10" Jolly.
The third and forth pictures are the 10" Jolly with the medium Orbit done with 1/2" diameter rope.