This is a factory 13 round magazine for the Smith & Wesson M&P Shield Plus.

According to Smith & Wesson, the M&P Shield Plus is the highest-capacity micro-compact pistol produced by Smith & Wesson. With this magazine, the Shield Plus firearm holds up to 13 + 1 rounds of 9mm ammunition. 

Double down on firepower and pick up a few of Shield Plus magazines at The Mag Shack.