This is the ProMag Ruger MAX-9 9mm 20-round magazine.

Maximize your Ruger MAX-9’s capacity with this high-quality 20-round magazine from ProMag!

Constructed from heat-treated steel and featuring an impact-resistant polymer floorplate, it will never let you down in terms of durability. Inside, you’ll find an injection-molded polymer follower and a chrome silicon wire spring that provide reliability to match. 

Whether your Ruger MAX-9 serves as your home defense, concealed carry, or range gun, this magazine is sure to please!  

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