My current cage for my male GTP is 24x24x20. I ordered it several years ago and they offered this cage shipped prebuilt. When I got it all I had to do was basically plug it in, put the perches in place, and place the doors in the slot.
The one on order for my female ETB is a 36x24x24.
I recently got a new tablet and though I thought it would work better with photobucket that is not the reality. PB just sucks. In my profile gallery are some pics of my GTP in its cage.