I have an M&P 9c with an Arredondo magazine extension. The extension was for the full size 9mm mags and fit the 9c mags perfectly. (pic below)
Today I picked up the M&P 2.0 9mm Compact. My understanding is that the magazines are compatible from the old M&P 9mm to the new 2.0, so would the base plate/extension be compatible as well? Anyone know?