This is the ProMag Smith & Wesson M&P .40 S&W 25 Round Extended Magazine.

SMI-A13 A double-stack 25-rd magazine for the Smith & Wesson M&P® series of pistols in caliber .40S&W.  Constructed from heat-treated blued-steel, with a follower, lock-plate, and base-plate molded from a proprietary DuPont® Zytel™ based black polymer.

• UPC Code: 708279011696
• Manufacturer: ProMag
• Manufacturer Part #: SMI-A13
• Type: Mag
• Caliber: 40 S&W
• Capacity: 25Rd
• Finish/Color: Blued
• Fit: Smith & Wesson M&P-40