ProMag Steel Pistol Magazine FN 509 9mm 20-Round Black 20RD. The springs are precision wound using heat-treated chrome silicon wire. Bases and followers are injection molded from polymers selected for their durability. The result is quality consistency durability and reliability. Specifications for ProMag Steel FN 509 9mm 20-Round Pistol Magazine: Manufacturer: ProMag Gun Model: FN 509 Caliber: 9mm Luger Magazine Capacity: 20 Round Features of ProMag Steel FN 509 9mm 20-Round Pistol Magazine Magazine body constructed of heat treated steel with black oxide finish Injection molded magazine follower Magazine spring formed from heat treated chrome silicone wire Package Contents: ProMag Steel FN 509 9mm 20-Round Pistol Magazine What firearm models does the manufacturer say ProMag Steel FN 509 9mm 20-Round Pistol Magazine is compatible with? The manufacturer says that ProMag Steel FN 509 9mm 20-Round Pistol Magazine is compatible with FN 509ProMag FNH-A13-20RD: Steel Pistol Magazine FN 509 9mm 20-Round Black