These Optima Choke tubes are available in internal and external versions for 12 gauge shotguns. They are longer and slimmer than conventional Mobilchoke tubes. Thanks to the elongated cone they minimize pellet deformation and improve shot patterns. The various versions are fully interchangeable on 12 gauge guns with Optima Bore barrels. These choke tubes are for 12 gauge shotguns with the Optima-Choke system only.