Shop › PROMAG FN 5.7 USG 30RD BLK PROMAG FN 5.7 USG 30RD BLK $50.99 ProMag Industries ProMag, Magazine, 5.7x28MM, 30 Rounds, Fits FN FiveSeven 20 Rounds Magazine With 10 Rounds Extension, Black FNH-A2 Quantity: Add To Cart Added! ProMag Industries ProMag, Magazine, 5.7x28MM, 30 Rounds, Fits FN FiveSeven 20 Rounds Magazine With 10 Rounds Extension, Black FNH-A2