The wheel comes completely apart for cleaning and once a month they recommend you oil the bearings so they do not seize. Each size comes in one color. They also have the option to add a sandpaper track that will trim the nails but to be perfectly honest with you, with the way a few of my girls run on them I would be worried they would rub their feet raw on the sandpaper. I imagine this isn't the case, I mean why would a company manufacture something that could do that.... someday I may try to put it in for just one day every few weeks but I still am a bit concerned.
Overall, a couple of my ratties still enjoy the Kaytee 12" Silent Spinner Wheels (they still have 1 in each cage) But a majority of them actually push and shove for their turn in Silent Runners, which are really quiet. I can only hear the patting of their feet and not any of the bearings.
To recap, The Silent Runner has only one color per size, you need to buy an additional cage attachment if you want to have it secured to your cage, optional track can be purchased – (Sandpaper for nails), it easy to clean, QUIET and is a nice 12" size with the option for a wider track. On average I have found it for around $28 online for the basic wheel. The only complaint is having to oil it monthly but worth it to make it last!
If you are planning on getting a wheel, make sure you invest and get the larger one (at least 12"). They will outgrow the smaller sizes in just a few months and can develop many complications from running on the wheel if not closely monitored. This can include but are not limited to spinal curvature (wheel tail), back injuries, nerve damage and even muscular injury.
**** I would rate the Exotic Nutrition Silent Runners - 4 out of 5 stars