This is the factory IWI US Masada 9mm 17-round magazine.

This magazine fits 9mm rounds and features a Hi-tensile spring and polymer follower for reliable feeding.

IWI MASADA 9mm polymer framed striker-fired pistol was developed in order to provide an advanced solution to the modern battlefield requirements. Much more than just another striker-fired pistol, the MASADA features a low profile barrel for reduced perceived recoil. Fully ambidextrous controls and enhanced ergonomics which provide a natural and instinctive pointing grip angle. Three interchangeable wrap around back-straps coupled with the deep beavertail enabling the MASADA pistol to fit a wide variety of hand sizes.