Samson manufacturing's +1 magazine extension not only allows you to carry more ammo, it also aids in your ability to clear malfunctions.It is designed to drop free without catching on the shooters hand, while the leading edge is contoured to facilitate one-handed reloads and act as a finger groove.The magazine extension features relief cuts to aid in extracting magazine to clear malfunctions and uses factory magazine spring.The replacement base plate retainer is designed to ensure positive feeding using the factory magazine spring.This model has a black hardcoat anodized finish and is compatible with s&w m&p shield 9/m&p shield 9 m20.Caliber: 9mm LugerCapacity: 7 & 8rdFinish: Hardcoat AnodizedModel: S&W M&P ShieldMaterial: 6061-T6 AluminumType: Magazine ExtensionModel Fit: M&P ShieldBrand Fit: S&WCapacity: 7 & 8