Models View all FN FiveseveN Magazine - 5.7x28mm 25 221 6 HK USP .40 Upper 47 321 5 FN FiveSeven frame 66 449 17 Sig SG 551 handguards, short rail, and charging handles 23 151 0 Sig SG series charging handles 9 79 2 Sig556 SWAT MLOK rail l 5 70 1