Comments: I have bought their Crittertrail One many years ago when they haven't published Crittertrail Two. I was satisfied with Crittertrail One, and now Crittertrail Two even amazed me more. They have added 4 buckles. Two on top and two in the bottom to make the plastic parts connection more firmly then before. Besides, the little apartment on the top is moveable now that makes it easier to be cleaned since hamsters usually take it as their main den. I also bought the Crittertrail Off To School (the Bus) and it connected well with the Crittertrail Two. The only three defects that could be improved are that the water bottle is too long for the mezzanine. It was too close to the mezzanine floor for my hamster to drink in a comfortable angle, even when he's no more than 2 months old and is short. So I use tissues to pile up the bottle; and the little apartment can only be connected with the plastic roof. It can't be separately connected with other extension even it is moveable; and the wheel will be too small to hamsters when they grow up. Other than these 3 little defects that my hamster hasn't found out yet, he basically lives happily in this cute cage and is crazy for the wheel. You might just need to use some tricks and reward to teach him use the tunnel to go on the mezzanine instead of climbing on the wire wall. We are still trying to figure out how to teach him not to urinate in the apartment.