There are elements of the Vengeance that recallseries, from the black rubberised top and steel bottom to the sniper button on the side that dramatically reduces DPI when hold down, and even the general look and feel.
Unlike the R.A.T. 7, though, this thing is cheap for a gaming mouse — AU$69. For the price, it's not bad, either, although we found it too wide for our liking. Those with big hands will likely appreciate it more.
Underneath the scroll wheel are DPI-increase and DPI-decrease buttons, with a meter in the middle. While we had no problems reaching the DPI up button, the DPI down button was placed too far down the mouse for comfortable on-the-fly switching.
There are two slim thumb buttons on the left, which Corsair does a good job of making sure are in range of your thumbs; you can just feel your way around quickly rather than having to look.
If you have a screwdriver or a 10c coin (a 20c coin will be too thick), you can flip the mouse over and remove up to three 4.5g weights in the bottom of the mouse. They're laid out in a V shape, meaning that not only the weight changes, but also, ever so minutely, so does the centre of gravity.