This is a factory POLYMER 18-round magazine in (Clear), for the USP9 Expert in 9mm with jet funnel. This magazine requires a Jet Funnel. The Jet Funnel has four primary roles in the USP40 Expert, added bottom weight, quicker reloading, expedited/ensured drop of magazines, and increased magazine capacity. This replacement magazine is a factory original from HK. 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.