This replacement magazine is a factory original from Smith & Wesson. Factory replacement parts are manufactured to the exact same specifications and tolerances and use the same manufacturing materials as the original parts which guarantees excellent fit and reliable operation. Keeping a few extra factory magazines around is never a bad idea; extra magazines save loading time at the range and also serve as a backup for those days when you simply cannot remember where you put your primary magazine. Note: Compact magazines WILL NOT work with full-size M&P or M&P9 2.0 Compact pistols