This evolution of the FN 509 Midsize" now featuring the FN Low Profile Optics Mounting System" gives you the option of direct mounting more than 10 different miniature red dot optics to your concealed carry pistol. The FN 509 Midsize MRD features a four-inch barrel and slide with optics mounting package" a midsized frame" and 10-round capacity. The improved controls aid in manipulation" the new improved texturing on the two included backstraps provides better recoil management" and a new flatter faced trigger allows for more controllable trigger press and cleaner break.