These chokes can be used on all Mobilchoke barrels. Made of high quality steel, they are of a great stress resistance due to heat treatments. They are subjected to a special coating that guarantees high protection to corrosion. Their shape has been studied in order to guarantee installation and de-installation without specific tools. The indication of the constriction is indicated by the stars at the top. These chokes are for 12 gauge shotguns only. WARNING:the Mobilchoke chokes are to be used exclusively on Mobilchoke compatible barrels.