The Kensington Expert Mouse Pro is a 10 button mouse for use with your PC or Mac computer. These are primarily used in DAW settings where it can be helpful to have a lot of buttons to help you perform all of the tasks necessary in a DAW, and do some in the quickest possible time. While Kensington certainly has the track-ball mouse down, to me this was one of their stepping stones to get there. I'm not sure how old the Kensington Expert Mouse Pro is, but it seems like it is one of the first mice that was put out my Kensington to feature the track ball. While this is certainly useful, to me it's not my favorite track ball mouse. Perhaps it's because I'm not used to the latest version of the Kensington track ball mouse, but I can't seem to get the hang of this one. It has the large track ball for movement in the middle as well as four large buttons to serve as your main mouse clicks. There is then a scrolling button and six more buttons on top which I've honestly never touched before. It is great that you can program this and assign whatever you want to each of the buttons, but since I don't own this one in particular I've never needed to take the time to do so. My main draw back with this one when compared to the newer Kensington Expert Mouse is that it doesn't have the scrolling wheel around the track ball and instead has the scrolling button above it. Of course I'm glad that they've made this adjustment in the newer models, but I don't think I could go back to using this one one a regular basis. In fact, I do prefer the standard Apple Mighty Mouse to this for it's ease of us. While it might be cheaper than the newest Expert Mouse, I'd recommend going with the latest model over the Expert Mouse Pro as to me they've improved upon this one a great deal.