There are two versions of the M&P 9 Pro.
One with 4.25" barrell and night sights.
One with 5 or 5.25" barrell and a green fiber optic front sight and Novak rear sight.
The PRO has a slghtly different trigger pull than the std M&P9. The Pro is about 4-1/2 lb pull versus the stds 6 lb pull.