Maximum overview at close quarters and optimum magnification at long range. This includes sealed boxes, or sealed accessories and manual/software included in boxes. Prism system: Schmidt-Pechan.
These things are incredible - it's nigh on impossible to keep them still enough to see anything, due to the magnification... This takes practice.
The only downside is that they cost 43% of my monthly mortgage repayment - but hey, you only live once :)