JARD Fin Brake 9mm Luger 3/4in 1/2x28 2in Length 4140 Steel Alloy Black. Comparatively traditional barrels or barrels without muzzle devices gas is predominately expelled inline with the barrel creating backward force that adds to recoil. Specifications for JARD Fin Brake: Manufacturer: JARD Color: Black Fabric/Material: 4140 Alloy Steel Threads per Inch: 1/2x28 Outer Diameter: 0.75 in Length: 2 in Package Contents: JARD Fin Brake JARD 3751: Fin Brake 9mm Luger 3/4in 1/2x28 2in Length 4140 Steel Alloy Black