"I bought the Super Pet CritterTrail X for my hamster, and I had the problem where she takes bedding up to the upper wheel and sleeps there. This was fine, but really annoying when she would run in it all the stuff would bounce around. But after I added this second wheel, she just runs in that instead and used to other wheel purely as a bed. I set things up differently then recommended because I couldn't stick anything out the top. It gets a bit wobbly, but if you set it up right it's plenty sturdy. Ichiko likes every part, but especailly the wheel. She runs in it alot, but it's really quiet."