Just the cage - No. With the extension - Yes. After owning 2 ferrets and having a large multilevel cage with hammocks and stations, I would never put them in something smaller. With the extension it would give them about the same room as the large cage. They are very active pets even when in their cage. The 4 hours of playtime is great but everyone knows they will not get it every day. Not saying anything about you but things happen, things come up, our lives go on with our pets but they will be there alone in their cage.
The cage is really nice and I do like it alot but I really think they need the extension or maybe something else like the extension for more room.
Check out my "Pet Pages" on Examiner.com for other pet related articles. I have one on ferret cages and the space they need. Check it out. I have others that talk about ferrets as well.