content: When I started working at Microsoft in 2000, I bought a Microsoft Optical trackball with a similar design to this one. That trackball has been discontinued..... So I started looking for a replacement for a nice ergonomical trackball. I came across this one. It offers everything the older Microsoft product used to offer. Ergonomical design, good for lots of mouse movements, precision.... The only thing I miss about the Microsoft trackball was the ability to spin the ball further when playing some games. That, however, is a minor issue, and I am not docking any stars for it.On the whole this sort of trackball ended carpal tunnel issues for me on my right hand. The same can be said for others I have recommended such trackballs to. They are really, really helpful for those of us who spend a lot of time at a computer. Highly recommended.