Shop › GEISSELE 10" SUPER MOD MK4 FED BLK GEISSELE 10" SUPER MOD MK4 FED BLK $382.50 Geissele Automatics MK4 Federal, Super Modular Rail, 10", M-LOK, Black, Barrel Nut Wrench Sold Separately (GEI-02-243), Gas Block Not Included 05-430B Quantity: Add To Cart Added! Geissele Automatics MK4 Federal, Super Modular Rail, 10", M-LOK, Black, Barrel Nut Wrench Sold Separately (GEI-02-243), Gas Block Not Included 05-430B