This replacement or spare magazine is compatible with your S&W M&P. It is constructed of heat treated steel with injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA.
Specifications:

Caliber	9mm Luger
Capacity	33
Finish	Blued
Model	S&W M&P 9
Material	Steel
Type	Detachable
Model Fit	M&P 9mm
Brand Fit	Smith & Wesson
Max Capacity	33