This is a DeSantis Gunhide Magazine Pouch known as the M38, model M38BJJJZ0.
The Nemesis(R) has already revolutionized pocket holsters" and now the Mag-Packer(R) is available for popular handgun magazines. This side pocket magazine holster will not move out of position in your pocket and allows proper positioning for your spare magazine. Available in black.
Features:
Pocket holster for spare magazine
Wide base helps keep the extra magazine in the proper place to draw each time