I bought this cage for my dwarf robo hamster, Benedict Cumberbatch. :) I got the cage out of the box to put it together, and there was a small crack on the bottom, since it was somewhere unseen and didn't look like it would leak anything, I kept it. However, once I saw the wheel, I immediately thought "oh no". In this picture and others I've seen online (tried to get a better grasp of the cage, the ONE pic doesn't do it justice) the wheel is smaller. I thought for sure my lil Benny wouldn't be able to make this thing go. I put him in his cage and he went right to it. He absolutely LOVED it, I could see at some points he'd have a lil trouble getting it to go, but once he got going, he could get up to speed. He would get going then stop, start, stop. I kept watching, and then noticed his lil foot would slip through the gap in the middle. I went off to Petsmart immediately, and bought him another wheel. When I got home he had learned to straddle the gap and get it going, but soon, once up to speed, his lil foot would slip. I also didn't want him straddling the gap constantly, because I feel this can't be good on his lil hips. (imagine running straddling a gap, lol) I took away the wheel and added the Den attachment I bought with this (you def need more room) he was so confused as to why his new toy was gone. I added his new free standing wheel, and he won't touch it. I'm sure he will learn, but it was sad taking it away from him. The water bottle....well....they could do better. There is a trick to it that's explained in the directions, but it only slows the leak, really. I would actually get the leak to stop after filling it, but then inserting it into its cradle slightly squeezed the bottle and it went to a very slow drip. Benny didn't like the small drips on the tunnel bottom, so he kicked bedding in to the tunnel. He almost packed the whole thing, so I had to dig it out. It was absorbing water from the bottle, emptying it and swelling. Once I dug some out, he did leave it alone. I left a lil in there, which absorbs the water, keeping the rest dry. I'll just have to change out that bedding often in the tunnel. I thought about getting a different bottle, but after I had to put another wheel, there's just no more room for extras in the main part of the cage. All in all, I do like this cage, its attractive and Benny seems to enjoy it too. the lock rings are a little tricky, and the instructions are just pictures, which I personally don't care for. I like something to read. Once I fiddled around I figured them out.You do have to be careful because parts of the cage are thin plastic, and I think anyone rough handed would break it! Haha! I found the hole openings to be the sturdiest. The main locking "Ovo" piece seems cheap and flimsy to me. I am afraid after many uses it may break, so I take extra care when opening and closing. I honestly think this cage is no good for an average sized hamster. It just wont be big enough. I still think my lil Benny is cramped with or without the wheel. I will def be buying more attachments. If you want to know my opinion on the Den attachment, I will have a review on that too. Enjoy!