FN 509 Midsize MRD 9mm Luger 4in Black Pistol - 10+1 Rounds - This ideal combination of a four-inch slide and barrel with a midsize frame retains full-sized pistol performance in an easily-concealed package. The 9mm pistol ships standard with a 10-round capacity and is compatible with all FN 509 magazines with use of a sleeve. FN Soft Case Interchangeable Backstraps FN Optics Mounting System Double Action