This is the ProMag Springfield Echelon 9mm 17-round magazine. 

If you’ve been on the hunt for an affordable spare magazine for your Springfield Echelon, look no further!

Constructed from heat-treated steel and featuring a black oxide finish, this magazine delivers superior corrosion resistance and durability. Internally, a chrome silicon wire spring and an injection-molded polymer follower keep the magazine feeding flawlessly. 

On top of it all, each magazine is made right here in the USA!

At this price, you might as well order a few!