I will tell you in my opinion, the 18x18 is too small.
Someone had convinced me that it was what I needed and
I bought it.
Then when I came home and set it up and put my conure
up to it, I realized that it would only work if NO TOYS WERE IN IT.
I decided immediately that it was not big enough.
So I returned the cage and ordered this one.
http://www.queencitypets.com/8002422.aspI received it and it is awesome! My conure took to it immediately
so I let him have it and I ordered ANOTHER ONE just this week.
Expecting it anyday for our new quaker coming home soon.
Knowing my conure which is same size as a quaker and knowing
how he loves his toys and room to flap, the 18x18 is just too small
in my opinion. My conure stays on top of his cage (the old one which
was 22x17 and now the new one which is 24 x 22 all the time)
but when he does go in and plays it was too small.
If you can afford to go bigger, I would recommend it.