Caution!
Sadly my hamster Nobbie broke his leg in the Habitrail hamster-weel that comes with the Habitrail Playground, and had to be put to sleep!
The accident happened when he got his tiny foot stuck in one of the several gaps between the two plastic sides that comes together to make out the wheel.
Prior to the accident I also observed how he found it a bit scary to use the wheel, as his poor hamster eyesight prevented him from always seeing where to step, as one side of the Habitrail-wheel is transparent .(All hamsters have poor eyesight.)
But it never occured to me that he could get his foot caught and breake his leg!
Other hamster-owners should be aware. Take the prowided Habitrail-wheel out,and give the hamster a different hamster-wheel!