NEW LEFT AND RIGHT  BOLT RAILS FOR BUILDING A M249, MK46 OR MK48 INTO A FULL AUTO OR SEMI AUTO. ONE PAIR (2) BOLT RAILS. THESE ARE THE BEST RAILS AVAILABLE AND ARE THE ONLY HARD NICKEL BORON PLATED RAILS AVAILABLE. HIGH QUALITY STEEL WITH THE REAR STOCK MOUNT AND EJECTION PORT DOOR AXIS PIN HOLES ALREADY DRILLED IN THE CORRECT POSITIONS. EASIEST RAILS TO INSTALL AND THE BEST QUALITY.