This is a ProMag SKS Magazine in 7.62x39mm. The ProMag provides fast, reliable ammo delivery, and this magazine holds 5 rounds and has a self-lubricating, polycarbonate follower with a precision wound, heat treated, chrome silicon spring. It has a removable base plate that allows easy disassembly for cleaning, and the magazine is made of polymer. ProMag magazines include a lifetime guarantee, if you ever have a problem with their magazines; simply return them to ProMag for replacement.