Semi-Auto Gas Operated shotguns are aluminum receiver and 12-20 and 28gau. are available. These model's are with double pistons for light and magnum shots. We have black and silver receivers and available with mobile choke also with extended mobile chokes. All parts are interchangeable for semi-auto models. Synthetic stock option is available. 2+1 , 4+1 and 7+1 magazine tubes are available.