The SpeedBead mount makes it easier to outfit all your favorite shotguns with a SpeedBead red dot sight, or move your FastFire I, II or III from your pistol or long gun for use during waterfowl season. The FastFire sight easily attaches to the mount with two screws. The mount is designed to fit between the receiver and rear stock on specific shotguns. Choose the mount from the list below:Fits: Stoeger 3500 12 Ga.