Mad Catz R.A.T. 6+ Optical Gaming Mouse Review
 

R.A.T. 6 has been recently reincarnated into the R.A.T. 6+ and features a very similar chassis, but an upgraded optical sensor (Pixart PMW3360). The Thumb Barrel adds an extra analog control layer, while the back cover can be adjusted as necessary in order to permit different grip types. Let’s not forget about the weight system (3x6G weights are pre-installed), that can be removed easily and the aluminum chassis that reinforces the build.

http://www.madshrimps.be/articles/article/1001117/