The FN Suppressor Booster Housing is machined from high-quality aluminum, this booster housing is designed for the FN Rush model suppressor for 9mm pistols. The booster housing contains the majority of the booster assembly, including the piston and the booster spring. Rely on factory-original FN parts and accessories to keep your suppressor in top shooting shape. FeaturesMajority of Booster AssemblyPistonBooster Spring