This drum replacement or spare magazine is compatible with your Sig Sauer MPX. It is constructed of DuPont Zytel polymer with injection molded mag follower and stainless steel wire. Made in the USA.
Specifications:

Caliber	9mm Luger
Capacity	50rd
Finish	Black
Model	Standard
Material	DuPont Zytel Polymer
Type
Model Fit	MPX
Brand Fit	Sig Sauer
Capacity	50