Fortis Manufacturing Low Profile Gas Block Stainless Steel. Don't want to mar your barrel installing the gas block? Neither do we So rock this gas block and put those concerns to bed. The Fortis LP gas block is designed for .750 gas seats and attaches to the barrel with two set screws. The gas block comes with a roll pin and two set screws. Specifications for Fortis Manufacturing Low Profile Gas Block: Manufacturer: Fortis Manufacturing Fabric/Material: 4140 Steel Condition: New Features of Fortis Manufacturing Low Profile Gas Block Two set screws 303 Stainless Steel 4140 Steel - Mod 2 Bead blasted finish 0.470in Set Screw Spacing Package Contents: Fortis Manufacturing Low Profile Gas Block Set Screw Fortis Manufacturing LPGB-SS-M2: Low Profile Gas Block Stainless Steel